Ico
Mi (ihfrinan" mm.
ELECTBO-CHEMISTRI
;. GOBE, F.K.S., LL.1).
m
ELECTRO-CHEMISTRY.
INORGANIC
BY
G. GORE, F.R.S., LL.D.,
Author of
" The Art of Scientific Discovery,"
"The Art of Electro- Metallurgy,"
The Principles and Practice of Electro-Deposition,
" The Scientific Basis of National Progress,"
etc., etc.
SECOND EDITION.
LONDON :
"THE ELECTRICIAN" PRINTING & PUBLISHING COMPANY (LIMITED),
I, Salisbury Court, Fleet Street, E.G.
NEW YORK :
W.J.JOHNSTON, " THE ELECTRICAL WORLD," 168-177, Potter Building.
1888.
INDEX TO CONTENTS.
PAGE
ACETATE OF CERIUM, ELECTROLYSIS OF 116
,, ,, LEAD ,, ,, 101
ALKALI METALS ELECTRO-DEPOSITED 2
ALLOYS, ELECTROLYSIS OF ? 7
,, ELECTROLYTIC 14
,, OF ZINC AND COPPER, ELECTRO-DEPOSI-
TION OF 112
,, OF ZINC, COPPER, AND NICKEL, ELECTRO-
DEPOSITION OF 113
ALUMINIUM, ELECTROLYSIS IN THE METALLURGY OF 1 19
SEPARATION OF 116
AMMONIA, ELECTROLYSIS OF 131
,, FIRST ELECTROLYSED 2
AMMONIUM AMALGAM, ELECTROLYTIC 132
CARBONATE, ELECTROLYSIS OF 133
CHLORIDE ,, ,, 133
SEPARATION OF ? 131
FLUORIDE, ELECTROLYSIS OF 133
NITRATE ,, 132
SULPHATE ,, ,, 134
AMMONIO CHLORIDE OF MAGNESIUM, ELECTRO-
LYSIS OF 114
ANALYSIS OF COPPER ORES BY ELECTROLYSIS 85
ANODE, MEANING OF THE TERM 4
ANODES, INSOLUBLE COATINGS ON 14
,, OF CARBON, ELECTROLYSIS WITH 47
ANTIMONIATE OF POTASSIUM, ELECTROLYSIS OF 60
ANTIMONY, ELECTRO-DEPOSITION OF EXPLOSIVE.. 55
,, SEPARATION OF 53
TERBROMIDE, ELECTROLYSIS OF 58
,, TERCHLORIDE , ...... 55
,, TERFI.UORIDE , , 55
,, TERIODIDE , 59
,, TEROXIDE , 54
,, TERSULPHIDE , 59
AQUEOUS AMMONIA 131
ARGENTIC CHLORATE , 73
,, CHLORIDE , 73
,, FLUORIDE ,, 72
,, NITRATE ,, 71
,, PEROXIDE 71
SULPHATE 74
ARGENTO POTASSIC CYANIDE ,, 75
,, SODIC SULPHATE ,, 74
ARSENIC, SEPARATION OF ,, 52
,, ACID, ELECTROLYSIS OF 53
,, TERCHLORIDE, ELECTROLYSIS OF 53
ARSENIDE OF HYDROGEN, ELECTROLYTIC SEPARA-
TION OF 53
AURIC TERCHLORIDE, ELECTROLYSIS OF 69
AURO-CYANIDE OF POTASSIUM ,, 69
BARIUM, SEPARATION OF 121
,, HYDRATE, ELECTROLYSIS OF 121
BATTERIES, VOLTAIC 25
BATTERY PROCESS OF ELECTRO-DEPOSITION 31
BlFLUORIDE OF TlN, ELECTROLYSIS OF IO5
BISMUTH, SEPARATION OF 60
CHLORIDE, ELECTROLYSIS OF 61
CYANIDE , ,, 61
FLUORIDE , ,, 61
IODIDE , ,, 61
NITRATE , ,, 60
OXIDE , 60
PEROXIDE,ELECTROLYTIC FORMATION OF 60
BISULPHIDE OF CARBON 51
BORATE OF SODIUM, ELECTROLYSIS OF 123
BORON, SEPARATION OF 48
,, COMPOUNDS, ELECTROLYSIS OF 48
PAGE
BROMIDES, CHLORIDES, AND IODIDES, ELECTRO-
LYSIS OF 45
BROMIDE OF CADMIUM, ELECTROLYSIS OF 109
,, IODINE 45
BROMINE, ELECTROLYTIC SEPARATION OF 43
,, ELECTROLYSIS OF OXIDES OF 44
BRUGNATELLI'S EXPERIMENTS IN ELECTRO-
GILDING 2
BRUGNATELLI FIRST DEPOSITS ZINC 2
CADMIUM, SEPARATION OF 109
,, COMPOUNDS, ELECTROLYTIC ANALYSIS
OF no
,, SELF-DEPOSITION OF 109
CAESIUM, SEPARATION OF 130
CALCIUM ,, ,, ng
CARBON ,, ,, 45
,, ANODES, ELECTROLYSIS WITH 47
CARBONATE OF AMMONIUM, ELECTROLYSIS OF 133
,, ,, POTASSIUM ,, ,
,, . ,, RUBIDIUM ,, ,
,, SODIUM ,, ,
,, STRONTIUM ,, ,
CARBONIC ANHYDRIDE ,, ,
CATHODE, MEANING OF THE TERM
CATHODES, CORROSION OF 12
CEASELESS MOLECULAR MOTION THEORY OF
VOLTAIC ACTION 23
CERIUM, SEPARATION OF 115
CHEMICAL ACTION, ELECTRICAL THEORY OF 24
,, CORROSION, ELECTROLYTIC BALANCE
OF 12
CHLORATE OF POTASSIUM, ELECTROLYSIS OF 129
,, ,, SILVER ,, ,, 73
CHLORIC ACID ,, ,, 43
CHLORIDES, BROMIDES, AND IODIDES, ELECTRO-
LYSIS OF 45
,, OF ALUMINIUM AND SODIUM, ELEC-
TROLYSIS OF 118
,, ,, AMMONIUM, ELECTROLYSIS OF 133
,, ,, ARSENIC, ANTIMONY, AND TIN,
ELECTROLYSIS OF 59
,, SARIUM, ELECTROLYSIS OF 121
129
130
123
120
47
4
II
M
i)
n
if
CHLORINE,
BISMUTH
, CADMIUM
, CAESIUM
, CALCIUM
, CERIUM
, COBALT
, COPPER
, IRON
, LEAD
, LITHIUM
, MAGNESIUM ANI
TROLYSIS OF
61
,, 109
,, ng
i "5
M 79
,, Q2
,, 122
AMMONIUM, ELEC-
, MANGANESE, ELECTROLYSIS OF 96
, MERCURY ,, 76
, NICKEL 87
, PALLADIUM ,, 64
, PLATINUM . . . 65
, POTASSIUM , I2 9
, RUBIDIUM ,, ... 130
, SILVER ... 73
, SODIUM ,, . . . 123
, STRONTIUM , I2
, SULPHUR "
, TIN, ELECTROLYS
, ZINC ,,
ELECTROLYTIC SEP
;is OF 106
A.RATIQN OF . . 42
iv
INDEX.
PAGE
CHLORINE, ELECTROLYSIS OF OXIDES OF 43
CHROMIUM, DEPOSITION OF 96
ELECTROLYTIC ANALYSIS OF COM-
POUNDS OF c7
CIRCUMSTANCES WHICH AFFECT THE AMOUNT OF
ELECTRO-CHEMICAL ACTION.. 9-10
WHICH AFFECT THE KlND OF
DEPOSIT 7-9
COBALT, ELECTRO-DEPOSITION OF 89
,, COMPOUNDS, ELECTROLYTIC ANALYSIS OF 91
,, CHLORIDE, ELECTROLYSIS OF 90
CYANIDE ,, 90
FLUORIDE . qo
bULPHATE ,, gi
,, PEROXIDE, ELECTROLYTIC FORMATION OF 90
COMPOUNDS OF CADMIUM, ELECTROLYTIC ANAL. OF no
,, CHROMIUM 97
,, COBALT
GLUCINUM
,, INDIUM
IRON
,, LEAD
MANGANESE
,, MOLYBDENUM
NICKEL
THALLIUM
TIN
URANIUM
, VANADIUM
, ZINC
CONDUCTIVITY OF LIQUIDS '. .". 3
CONDUCTION IN ELECTROLYTES WITHOUT DECOM-
POSITION 79
COPPER, SEPARATION OF 78
,, ELECTROLYTIC PURIFICATION OF 82
,, ETCHED BY ELECTROLYTIC ACTION 83
,, REFINED BY ,, ,, 83
,, NITRIDE, ELECTROLYTIC FORMATION OF 79
ORES ANALYSED BY ELECTROLYSIS 85
,, AND TIN ALLOYS, SEPARATION OF 108
ZINC ,, 112
ZINC, AND NICKEL ALLOY, ELECTRO-
DEPOSITION OF 113
CORROSION OF CATHODES 12
CRYSTALS OF TIN FORMED BY ELECTROLYSIS 108
CRUICKSHANK'S EXPERIMENTS 2
CUPRIC CHLORIDE, ELECTROLYSIS OF 79
FLUORIDE ,, 79
,, NITRATE ,, ,, 79
,, SULPHATE ,, ,, 81
CUPROSO POTASSIC CYANIDE, ELECTROLYSIS OF.. 84
CURRENT, STRENGTH OF 27
RELATIVE AMOUNTS OF, PRODUCED BY
DIFFERENT METALS 29
CYANIDE OF BISMUTH, ELECTROLYSIS OF 61
CAESIUM I31
COBALT ,, 90
COPPERANDPOTASSIUM.ELECTROL.OF 84
GOLD 69
PALLADIUM, ELECTROLYSIS OF 65
POTASSIUM ,, ,, 129
SILVERAND POTASSIUM, ELECTROL.OF 75
ZIN C ,, 112
DAVY'S DISCOVERY OF THE ALKALI METALS 2
DECOMPOSABILITY OF ELECTROLYTES 6
DEFINITE ELECTRO-CHEMICAL ACTION 10
DEFINITION OF ,, ,, 3
DENSITY OF CURRENT 28
ELECTRO-DEPOSITS 8
DEPOSITS, CIRCUMSTANCES AFFECTING KIND OF
ELECTRO 7-9
,, CIRCUMSTANCES AFFECTING AMOUNT
OF ELECTRO 9-10
DESILVERISING LEAD 103
DIDYMIUM, SEPARATION OF 115
DISCOVERY OF THE VOLTAIC BATTERY 2
,, ,, ,, ALKALI METALS 2
,, DEFINITE ELECTRO-CHEMICAL
ACTION 2
DISTRIBUTION OF CURRENT IN ELECTROLYTES
DIVIDED ELECTROLYSIS
15
ELECTRICAL THEORY OF CHEMISTRY 24
ELECTRO-CHEMICAL ACTION, DEFINITION OF 3
,, ,, ,, CHIEF CONDITIONS OF 3
,, THEORIES OF 20-21
ELECTRO-CHEMISTRY OF INDIVIDUAL SUBSTANCES 32
ELECTRODES, MEANING OF THE TERM 4-5
,, POLARISATION OF 16
UNEQUAL ELECTRIC ACTION AT 16
ELECTRO-GILDING UPON SILVER FIRST OBSERVED 2
ELECTROMOTIVE FORCE 25-26
ELECTROLYSIS, DIVIDED 15
,, DEPENDENCE OF, UPON LIQUID
DIFFUSION 18
,, INFLUENCE OF MAGNETISM UPON 10
,, ,, TEMPERATURE 10
RELATION OFjToCHEMiCAL ACTION n
LIMITS OF 7
OF ALLOYS ? 7
INDIVIDUAL SUBSTANCES 3 2
,, RELATIONS OF, TO HEAT 19
,, SECONDARY EFFECTS OF 13
,, VISIBLE PHENOMENA OF 4
ELECTROLYTES, DISTRIBUTION OF CURRENT IN .. 30
ELECTROLYTIC ALLOYS 14
,, ANALYSIS FIRST SUGGESTED 2
,, ARRANGEMENTS 30
BALANCE OF CHEM. CORROSION.. 12
AND VOLTAIC ACTION, CONNEC-
TION BETWEEN 22
ANDVOLTAIC ACTION.DlSTINCTION
BETWEEN 21
DEPOSITS, PURITY OF 15
,, DIFFUSION OF LIQUIDS 18-19
,, ETCHING OF COPPER 83
,, MOVEMENTS OF MERCURY 2-5-77
,, SEPARATION OF HYDROGEN 33
SOUNDS 5-77
,, TRANSFER FIRST OBSERVED 2
EXPLOSIVE ANTIMONY, ELECTRO-DEPOSITION OF.. 55
FARADAY'S DISCOVERY OF DEFINITE ELECTRO-
LYTIC ACTION 2-10
FERRATE OF POTASSIUM, ELECTROLYSIS OF 94
FERRI-CYANIDE OF POTASSIUM ,. ,, 130
FERRIC CHLORIDE ,', 92
FERRO-CYANIDE OF IRON ,, , 94
,, POTASSIUM , 130
FERROUS CHLORIDE ,, , 90
SULPHATE , 93
FLUORIC ACID ,, , 40-41
FLUORIDE OF ALUMINIUM ....... 118
,, ,, AMMONIUM ,, , 133
,, ,, ANTIMONY ,, , 55
,, ,, BISMUTH ,, , 61
CALCIUM ,, , 119
COBALT , 90
COPPER , 79
GOLD , 68
,, LEAD ,, , 101
LITHIUM ,, , 121
MANGANESE ,, , 95
NICKEL ,, , 87
PALLADIUM ,, , 63
POTASSIUM ,, , . . 125-128
SILVER ,, , 72
SODIUM ,, , 122
STRONTIUM ,, , 120
TIN 105
,, URANIUM ,, 97
FLUORINE, ELECTROLYTIC SEPARATION OF? 40
GALLIUM, SEPARATION OF 1 16
GERBOIN'S EXPERIMENTS 2
GLUCINUM, SEPARATION OF . . 119
GOLD, SEPARATION OF 68
GOLD FLUORIDE, ELECTROLYTIC FORMATION OF.. 68
GOLDING BIRD'S EXPERIMENTS 3
INDEX.
PAGE
HEAT : ITS RELATION TO ELECTROLYSIS 19-20
HENRY'S EXPERIMENTS 2
HISINGER AND BERZELIUS DISCOVER ELECTRO-
LYTIC TRANSFER : 2
HISTORY OF ELECTRO-CHEMISTRY i
HYDRATE OF BARIUM, ELECTROLYSIS OF 121
,, ,, POTASSIUM ,, ,, 124
SODIUM 122
HYDRIC SULPHIDE, SEPARATION OF, BY ELECTRO-
LYSIS 50
HYDRIDE OF SILICON, SEPARATION OF, BY ELEC-
TROLYSIS 49
HYDRIODIC ACID, ELECTROLYSIS OF 44
HYDROBROMIC ACID ,, 44
HYDROCHLORIC ,, ,, 42
HYDROFLUORIC ,, ,, ,, 40-42
HYDROGEN, ELECTRO-DEPOSITION OF 33
,, IN ELECTROLYTIC DEPOSITS 34
,, " EXPLOSIVE ANTIMONY "? 35
,, PEROXIDE, ELECTROLYSIS OF 37
INDIUM, SEPARATION OF 105
,, COMPOUNDS, ELECTROLYTIC ANALYSIS OF 105
INSOLUBLE COATINGS ON ANODES 14
IODIC ACID, ELECTROLYSIS OF 44
IODIDES, BROMIDES, AND CHLORIDES, ELECTROL. OF 45
IODIDE OF BISMUTH ,, ,, 61
,, PALLADIUM ,, ,, 64
,, POTASSIUM ,, ,, 129
IODINE, SEPARATION OF 44
,, ELECTROLYSIS OF OXIDES OF 45
IONS, MEANING OF THE TERM 4
,, TRANSPORT OF 19
IRIDIUM, SEPARATION OF 62
IRON ,, 91
COMPOUNDS, ELECTROLYTIC ANALYSIS OF .. 94
CHLORIDE, ELECTROLYSIS OF 92
FERROCYANIDE ,, ,, 94
SULPHATE ,, ,, 93
RENDERED BRITTLE BY ELECTROLYSIS 35
ISOLATION OF FLUORINE ? 40
LANTHANUM, SEPARATION OF 115
LAW OF DEFINITE ELECTROLYTIC ACTION 2-10
LEAD, SEPARATION OF 100
COMPOUNDS, ELECTROLYTIC ANALYSIS OF . . 103
ACETATE, ELECTROLYSIS OF 101
CHLORIDE ,, ,, 101
FLUORIDE ,, ,, 101
NITRATE ,, ,, 100
DESILVERISED BY ELECTROLYSIS ? 103
PEROXIDE, ELECTROLYTIC FORMATION OF 2-102
LIMITS OF ELECTROLYSIS 7
LIQUID DIFFUSION, RELATION OF, TO ELECTRO-
LYSIS 18-19
LIQUID ELECTRODES, MOVEMENTS OF 5
LIQUIDS, ELECTRIC CONDUCTIVITY OF 3
LITHIUM, SEPARATION OF 121
MAGNESIUM, SEPARATION OF , 113
ELECTRO-METALLURGY OF 114
MAGNETISM, ITS EFFECT UPON ELECTROLYSIS.... 10
MANGANESE, SEPARATION OF 94
COMPOUNDS, ELECTROLYTIC ANAL. OF 96
CHLORIDE, ELECTROLYSIS OF
FLUORIDE ,, ,,
SULPHATE
PEROXIDE, ELECTROLYTIC FORMA-
TION OF
MEASUREMENT OF CONDUCTION RESISTANCE
,, ,, ELECTROMOTIVE FORCE
,, QUANTITY OF CURRENT
,, ,, STRENGTH ,, ,,
MERCURY, SEPARATION OF 75
MERCURIC CHLORIDE, ELECTROLYSIS OF 76
,, NITRATE ,, ,, 7 6
,, POTASSIO-CYANIDE,, 77
METALLO-CHROMY 103
METALS, SELF-DEPOSITION OF 31
MINERALS, DECOMPOSITION OF, BY ELECTROLYSIS 50
MODES OF PRODUCING VOLTAIC CURRENTS 23
PAGE
MOLECULAR MOTION THEORY OF VOLTAIC ACTION 23
MOLYBDENUM, SEPARATION OF 99
COMPOUNDS, ELECTROLYTICAL ANAL. OF 100
MOLYBDIC ACID, ELECTROLYSIS OF 99
MOVEMENTS OF MERCURY BY ELECTROLYSIS 2-5-77
NICKEL, SEPARATION OF 86
,, COMPOUNDS, ELECTROLYTIC ANALYSIS OF 89
CHLORIDE, ELECTROLYSIS OF 87
FLUORIDE ,, ,, 87
,, NITRATE ,, ,, 87
SELENATE 89
,, SULPHATE ,, ,, 88
ZINC, AND COPPER ALLOYS, ELECTRO-
DEPOSITION OF 113
NICHOLSON AND CARLISLE DECOMPOSE WATER . . 2
NITRATES, ELECTROLYSIS OF 38
NITRATE OF AMMONIUM, ELECTROLYSIS OF 132
,, BARIUM 121
,, BISMUTH 60
,, CERIUM 115
,, COPPER 79
,, LEAD 100
MERCURY 76
,, NICKEL 87
,, PALLADIUM 62
POTASSIUM 125
,, SILVER 71
NITRIC ACID, ELECTROLYSIS OF 39
NITRIDE OF COPPER, ELECTROLYTIC FORMATION OF 79
NITROGEN, ELECTROLYTIC SEPARATION OF 38
,, ELECTROLYSIS OF OXIDES OF 38
NOBILI FIRST ELECTRO-DEPOSITS PEROXIDE OF LEAD 2
NOMENCLATURE 4
NORWEGIUM, SEPARATION OF 114
OSMIUM, SEPARATION OF 61
OSMIC ACID, ELECTROLYSIS OF 61
OXIDE OF BISMUTH
OXIDES OF BROMINE ,
CHLORINE,
,, IODINE ,
NITROGEN,
,, ,, PHOSPHORUS
OXYGEN, SEPARATION OF
OZONE
PAETZ AND VAN TROOSTVIK'S EXPERIMENTS 2
PALLADIUM, SEPARATION OF 62
CHLORIDE, ELECTROLYSIS OF 64
CYANIDE
IODIDE
NITRATE ,, ,,
FLUORIDE, ELECTROLYTIC FORMATION
OF
PEROXIDE
PASSIVE STATE OF METALS 39
PERCHLORATE OF SILVER, ELECTROLYSIS OF 74
PERCHLORIDE OF IRON ,, 9 2
PEROXIDE OF BISMUTH, ELECTROLYTIC FORMA-
TION OF 60
COBALT 9
LEAD ,, 2-102
MANGANESE 95
PALLADIUM ,,
SILVER ,, 2-70
HYDROGEN, ELECTROLYSIS OF 37
PERS'ULPHUR'I'C ACID, SEPARATION OF 51
PHOSPATE OF SODIUM, ELECTROLYSIS OF 124
PHOSPHORIC ACID, ELECTROLYSIS OF 52
PHOSPHORUS, ELECTROLYTIC SEPARATION OF 5 2
,, CHLORIDE, BROMIDE, AND IODIDE OF 52
PHYSICAL STATES OF ELECTRO DEPOSITS 8-9
PLATINIC CHLORIDE, ELECTROLYSIS OF 67
PLATINUM, SEPARATION OF 65
,, FLUORIDE, ELECTROLYTIC FORMATION
OF 66
PLUMBATE OF POTASH, ELECTROLYSIS OF 102
PLUMBIC ACETATE ,, 102
CHLORIDE ,, 101
vi
INDEX.
P.AGE
PLUMBIC FLUORIDE, ELECTROLYSIS OF 101
,, NITRATE, ,, , 100
,. PEROXIDE ,, ,, 102
POLARITY 25
POLARISATION OF ELECTRODES 16
POTASSIUM, SEPARATION OF 2-124
ANTIMONIATE, ELECTROLYSIS OF 60
,, CARBONATE 129
,, CHLORATE 129
,, CHLORIDE 129
,, CYANIDE 129
,, FERRICYANIDE .... 130
,, FERROCYANIDE 130
,, FLUORIDE 125-128
,, HYDRATE .... 124
,, IODIDE .... 129
,, NITRATE 125
PLUMBATE 102
POTENTIAL 25
PREPARING SOLUTIONS FOR ELECTROLYSIS 32
PRESSURE, EFFECT OF, UPON ELECTROLYSIS OF
WATER 37
PROCESS, SIMPLE IMMERSION 30
,, SINGLE CELL 31
PURIFICATION OF COPPER BY ELECTROLYSIS 82
PURITY OF ELECTRO-DEPOSITED METALS 15
QUANTITY OF CURRENT 28
,, ,, FROM DIFFERENT METALS 29
REFINING COPPER BY ELECTROLYSIS 83
RELATIONS OF ELECTRO-CHEMICALS TO ORDINARY
CHEMICAL ACTION 1 1
RESISTANCE 27
RHODIUM, SEPARATION OF 62
RlTTER FIRST DEPOSITS PEROXIDE OF SlLVER 2
RUBIDIUM, SEPARATION OF 130
RUTHENIUM ,, ,, 62
SECONDARY EFFECTS OF ELECTROLYSIS 13
SELKNATE OF NICKEL, ELECTROLYSIS OF 89
SELENIUM, ELECTROLYTIC SEPARATION OF 51
SELF-DEPOSITION OF METALS 31
SEPARATE CURRENT PROCESS 31
SEPARATION OF FLUORINE 40
SILICIC ANHYDRIDE, SEPARATION OF, BY ELECTRO-
LYSIS 49
SILICON, SEPARATION OF, BY ELECTROLYSIS? 48-49
SILVER, SEPARATION OF 70
FIRST COATED WITH COPPER BY ELECTRO-
LYSIS 2
,, PERCHLORATE, ELECTROLYSIS OF 74
,, PEROXIDE, ELECTROLYTIC FORMATION OF 2-70
SIMPLE IMMERSION PROCESS 30
SINGLE CELL PROCESS 31
SODIUM, SEPARATION OF 2-122
,, BORATE, ELECTROLYSIS OF 123
,, CARBONATES ,, ,, 123
CHLORIDE ,, ,, 123
,, FLUORIDE ,, ,, 122
,, PHOSPHATE ,, ,, 124
,, SULPHATE ,, ,, 123
TUNGSTATE , 99
SOLUTIONS; How PREPARED FOR ELECTROLYSIS.. 32
SOUNDS EMITTED DURING ELECTROLYSIS 5-77
SOURCE OF VOLTAIC CURRENT 23
STANNIC CHLORIDE 106
STANNOUS ,, ELECTROLYSIS OF 106
FLUORIDE , 105
STRENGTH OF CURRENT 28
STRONTIUM, SEPARATION OF 120
SULPHATE OF AMMONIUM, ELECTROLYSIS OF 134
CERIUM
COBALT
COPPER
GALLIUM
IRON
MANGANESE
NICKEL
SILVER
.... 116
PAGE
123
x 4
SULPHATE OF SODIUM, ELECTROLYSIS OF
,, ,, THALLIUM, ,, ,,
ZINC ,, ...... I"
SULPHIDE, HYDRIC, ELECTROLYTIC FORMATION OF 50
SULPHIDES OF ARSENIC, ANTIMONY, AND TIN,
ELECTROLYSIS OF ............ 60
SULPHUR DIOXIDE, ELECTROLYSIS OF ............ 50
,, ELECTROLYTIC SEPARATION OF ........ 49-5
SULPHURIC ACID, ELECTROLYSIS OF .............. 50
SULPHUROUS ANHYDRIDE ,, .............. 5
SULZER'S EXPERIMENTS ....................... i
TEMPERATURE : ITS INFLUENCE ON ELECTROLYSIS 10
TELLURIUM, SEPARATION OF .................... 51
,, CHLORIDE, ELECTROLYSIS OF ........ 5 2
,, FLUORIDE ,, , ......... 52
TERBROMIDE OF ANTIMONY, ELECTROLYSIS OF .. 58
TERCHLORIDE OF ,, ,, ,, .. 55
,, ,, ARSENIC ,, .. 53
GOLD .. 69
TERIODIDE OF ANTIMONY ,, ,, .. 59
TERMS EMPLOYED IN ELECTRO-CHEMISTRY ____ 4
TEROXIDE OF ANTIMONY, ELECTROLYSIS OF ...... 54
TERSULPHIDE OF ,, ,, ,, ...... 59
TETRACHLORIDE OF TIN ........................ 106
,, PLATINUM, ELECTROLYSIS OF 67
THALLIUM, SEPARATION OF .................... 104
,, COMPOUNDS, ELECTROLYTIC ANAL. OF 105
,, SULPHATE, ELECTROLYSIS OF ........ 104
THEORIES OF ELECTROLYSIS .................... 21
THEORY OF VOLTAIC ACTION .................... 23
THORIUM, SEPARATION OF ...................... 114
TIN ...................... 105
COMPOUNDS, ELECTROLYTIC ANALYSIS OF ---- 109
,, CHLORIDE, ELECTROLYSIS OF ................ 106
,, BIFLUORIDE ,, ,, ............... 105
,, CRYSTALS FORMED BY ELECTROLYSIS ........ 108
TIN AND COPPER ALLOYS, SEPARATION OF ...... 108
TITANIUM, SEPARATION OF .................... 49
TRANSPORT OF IONS ............................ 19
TUNGSTATE OF SODIUM, ELECTROLYSIS OF ...... 99
TUNGSTEN, SEPARATION OF .................... 98
UNIT OF CONDUCTION-RESISTANCE .............. 26
,, ,, ELECTROMOTIVE FORCE ................ 27
,, DENSITY OF CURRENT ................ 28
,, ,, QUANTITY ,, ................ 28
,, ,, STRENGTH ................ 27
URANIUM, ELECTRO-DEPOSITION OF ............ 97
COMPOUNDS, ELECTROLYTIC ANAL. OF 98
,, SOLUTIONS, ELECTROLYSIS OF ---- 97-98
VANADIUM, SEPARATION OF ....................
,, COMPOUNDS, ELECTROLYTIC ANAL. OF
VOLTA'S GREAT DISCOVERY ....................
VOLTAIC ACTION, THEORY OF ..................
AND ELECTROLYTIC ACTION, INTIMATE
CONNECTION BETWEEN ............
, , AND ELECTROLYTIC ACTION, DISTINCTION
BETWEEN ..........................
BATTERIES ............................
CURRENTS ...........................
SOURCE OF ..................
,, MODES OF GENERATION ----
,, SERIES ......................
WATER, ELECTROLYSIS OF ...................... 2-36
WOLLASTON FIRST DEPOSITS COPPER UPON SILVER 2
ZINC, SEPARATION OF .......................... 2-110
COMPOUNDS, ELECTROLYTIC ANALYSIS OF 113
SELF-DEPOSITION OF .................... no
CHLORIDE, ELECTROLYSIS OF .............. in
POT ASSIC CYANIDE ,, , ............... 112
SULPHATE ,, ,, .............. in
ANDCOPPERALLOYS,ELECTRO-DEPOSITIONOF 112
COPPER AND NICKEL ,, ,, ,, 113
ZIRCONIUM 49
ZOSIMUS'S EARLY EXPERIMENTS i
INTRODUCTION.
No separate treatise on Electro-Chemistry exists in the
English language. The facts relating to the subject lie
scattered in a great number of books and periodicals.
Perceiving the utility of such a treatise, I have collected
the numerous truths yet discovered in the subject and
arranged them in consecutive order in the following pages.
The treatise is not, however, merely a systematic and
orderly collection of facts, but contains also brief descriptions
of the known laws and general truths which underlie them.
The scope of the treatise is limited to the Electro-
chemistry of what is conventionally termed mineral com-
pounds. Whilst nearly all the ordinary liquid and liquefiable
salts belonging to " inorganic " chemistry have been subjected
to the action of an electric current, and the effects observed,
the influence of the current upon " organic " substances,
although a subject of great extent, has hitherto been com-
paratively little investigated, and the facts as yet obtained
in " organic " electrolysis are of an isolated and fragmentary
character.
As the purpose for which the matter of this book was
originally written rendered it advisable to limit the scope
viii INTRODUCTION.
of the subject and to compress a large amount of informa-
tion into a small compass, the laws and principles of the
subject are only briefly illustrated.
The present treatise is essentially a Scientific one, and all
facts and information of a purely Technical character have
been purposely omitted.
G. GORE.
Birmingham, 1885.
ELECTRO-CHEMISTRY.
INORGANIC.
THE present series of articles is intended to contain, in syste-
matic order, the chief principles and facts of electro-chemistry,
and to supply to the student of electro-plating or electro-metal-
lurgy a scientific basis upon which to build the additional prac-
tical knowledge and experience of his trade. As the series is
a purely scientific one, it will not include such technical details
or particulars as will enable the practical worker to obtain
perfect workshop results ; these may be obtained from tech-
nical books on electro-metallurgy, combined with actual work-
shop experience. A scientific foundation, such as is here given,
of the art of electro-metallurgy, is, however, indispensable to
the electro-depositor who wishes to excel in his calling, and
should be studied previously to and simultaneously with prac-
tical working. It is partly in consequence of deficiency of
such fundamental knowledge by the British workman (and
partly to the undue pursuit of wealth by his employers) that
English manufactures are gradually being transferred to foreign
lands. Whilst, also, the series of articles will contain the chief
facts upon which the comparatively new art of electro-che-
mical analysis of minerals and alloys is based, it will not supply
the technical details necessary for the accurate quantitative
determination of metals by electro-chemical processes; refe-
rences to sources of such information will, however, be given.
The molecular weights of substances, as given at the heads
of the paragraphs, are in nearly all cases those of the anhy-
drous ones -, for those of the hydrated compounds the student
is referred to books on chemistry.
History. The history of electro-chemistry requires only a
brief description. Ages before the discovery of voltaic elec-
tricity it was known that various metals, by being simply im-
mersed in metallic solutions, became coated with the metal
previously dissolved in the liquid. Thousands of years ago
Zosimus mentioned the deposition of bright metallic copper
upon iron immersed in a solution of a salt of copper. In the
year 1752 Sulzer remarked, "If you join two pieces of lead
and silver, so that they shall be upon the same plane, and
then lay them upon the tongue, you will notice a certain
(2 )
taste resembling that of green vitriol, while each piece apart
produces no such sensation." Paetz and Van Troostvik also,
in the year 1790, decomposed water by passing electric sparks
through it by means of very fine gold wires.
It was, however, the discovery by Volta, in 1799, of his
electric battery which gave the first great impulse to electro-
chemistry. By means of it Nicholson and Carlisle first decom-
posed water by means of a voltaic current from a battery on
May 2nd, 1800 ; and soon afterwards Dr. Henry, of Man-
chester, decomposed nitric and sulphuric acids, and also-
ammonia by similar means. During the next year Dr.
Wollaston discovered that if a piece of silver in connection
with a more positive metal be put into a solution of copper
the silver becomes coated with copper, which coating will
stand the operation of burnishing. In the year 1801 Gerboin
also first noticed the movements produced in mercury during
the act of electrolysis. In 1803 Hisinger and Berzelius dis-
covered that by means of a voltaic current the elements of
water and of neutral salts were transferred to the respective
polar wires immersed in the liquid ; and Cruickshank, about
the same time, observed the electro-deposition of lead, copper,
and silver upon one of the polar wires (the one connected
with the zinc end of the battery) immersed in solutions of
salts of those metals, and was thus led to suggest the analysis
of minerals by means of the voltaic current. In 1805 Bru-
gnatelli observed the electro-deposition of gold upon silver
when the former was made the negative pole in a solution of
ammoniuret of gold ; he also discovered the electro-deposition
of zinc.
The most striking proof, however, of the great chemical
power of the electric current was the discovery, on October
the 6th, 1807, by Sir Humphrey Davy, of the electrolytic
decomposition of potash and soda, and the liberation of their
respective metals, by a current from a voltaic battery com-
posed of 274 cells. In 1826 Nobili discovered the deposition
of peroxide of lead in films of beautiful colour upon the
platinum plate which conveyed a voltaic current into a
solution of acetate of lead, and Bitter subsequently dis-
covered the deposition of peroxide of silver from a solution
of argentic nitrate under similar conditions. In 1834 Faraday
discovered the important truth that, by the passage of an
electric current through an undivided series of solutions of
various metallic salts, or through those salts whilst in a
state of fusion, the quantity of each salt decomposed was in
direct proportion to the amount of current. Also that the
Quantities of the different metals dissolved or deposited were
in definite proportions by weight, and that those proportions
were identical with those of tho ordinary chemical equivalents
of those nietals ; and he thus established the law of definite
( 3 )
electro-chemical action. And in 1837 Dr. Golding Bird suc-
ceeded in decomposing, by means of feeble voltaic currents,
solutions of the chlorides of sodium and potassium, and
depositing their respective metals into mercury.
As the subject of electro-chemistry is a very large one, it
is only briefly treated in the following series of articles. The
general principles and phenomena will be first explained, and
then will follow an account of the action of the current upon
individual substances.
Definition of Electro-Chemical Action. Electro-chemical
action is chemical change produced by means of an electric
current, and usually consists of the decomposition of a com-
pound liquid, the liquid being resolved into its constituent
parts in certain definite proportions by weight ; it is also
often attended by chemical union of a metal, in certain definite
proportions by weight, with one of the elements of the liquid.
It is usually limited to combinations of conducting substances
only.
Chief Conditions of Electro-Chemical Action. The chief
conditions are that the substance must be a liquid, a compound
body, a conductor of electricity, and traversed by the current.
The liquids decomposable by a current are usually composed 1
of two elementary substances, the one being a metal and the
other a non-metal. Liquid alloys, or liquids composed of two
non-metallic elements, are not usually decomposed. Mixtures
of compounds in solution are commonly decomposed more
easily than solutions of single compounds ; for instance, water
containing sulphuric acid is decomposed much more readily
than water alone.
All the products of electrolysis are set free in an almost
infinitely thin layer at the immediate surfaces of the conductors
at the parts where the current enters and leaves the liquid.
The electro-negative products, such as the non-metallic
elements and acids, are either liberated at or combine with
the conductor, by which the current enters the liquid, and
the electro-positive ones, such as metals and alkalies, are
liberated at or combine with the conductor by which the
current leaves the liquid. The behaviour of individual
combinations of metals and liquids will be subsequently
described.
Conductivity of Liquids. Liquids present an extremely
wide range of conducting power ; whilst some completely
resist the passage of a current from 10,000 voltaic cells in,
single series, others transmit freely the current from a single
element. Amongst the non-conducting ones may be included
all oils, benzine, petrolene, bisulphide of carbon, the liquid
chlorides of carbon, terchloride and pentachloride of phos-
phorus, terchloride of arsenic, pentachloride of antimony,
B 2
(4)
tetrachloride of tin, zinc-ethyl, perfectly pure water, bromine,
various liquefied gases, including chlorine, carbonic anhy-
dride, cyanogen, sulphurous anhydride, hydrochloric, hydro-
bromic, and hydriodic acids ; nearly all melted fats and resins,
fused iodine, sulphur, phosphorus, realgar, &c. Amongst the
inferior conductors are aqueous solutions of gum, sugar,
ammonia, boracic acid, mercuric cyanide, and alcoholic solu-
tions of metallic salts ; also melted boracic acid and fused
glass. Amongst the best conducting compound liquids are
aqueous solutions of salts of the alkali metals, and of copper,
silver and gold, and especially certain fused salts, e.g., argentic
fluoride and chloride.
According to Hittorf, the degree of resistance of a liquid to
electrolysis is dependent upon the difficulty with which the
molecules exchange their constituents. Those which have
active chemical properties should therefore conduct the best.
Bleekrode contests this view.
Nomenclature. The electrical decomposition of liquids is
termed electrolysis ; the conductor by which the current is said
to enter the liquid is called the anode, and the one by which
it leaves it is termed the cathode. The products into which
the liquid is decomposed are called ions, those which appear
at the anode being anions, and those at the cathode cations.
Non-metals, acids, and peroxides are usually anions, while
metals and alkalies are cations ; electro-negative bodies, there-
fore, usually appear at the anode or positive pole, and electro-
positive ones at the cathode or negative pole. The same
elementary substance, however, may appear at the positive
pole in one case, and at the negative pole in another, according
to the circumstance whether the body it is combined with is
more positive or more negative than itself. For instance,
iodine, when combined with a more positive body, such as
hydrogen in hydriodic acid, appears at the anode ; but when
combined with a more negative one, such as oxygen in iodic
acid, it appears partly at the cathode. Sulphur in suitable
different combinations exhibits the same variation. Hydrogen
is almost the only gaseous cation.
Visible Phenomena of Electrolysis. The phenomena
usually seen in a liquid during electrolysis are at the anode,
corrosion with or without solution of the anode, gas is evolved,
the anode acquires an insoluble coating, &e. In some liquids
the anode becomes fragile, and falls to powder ; in others it
flies to pieces, but this is a rare case. Silver in dilute hydro-
fluoric acid is an example of the former, and wood charcoal in
anhydrous hydrofluoric acid is an instance of the latter. At
the cathode, a soluble substance is set free and dissolves, or a
gas, a liquid, or a solid is liberated, and is either absorbed by
the cathode, or adheres to it, or is dissolved by the liquid, or
(5 )
escapes. The layers of liquid also in contact with the
electrodes frequently alter in specific gravity, that at the
anode usually becomes heavier, and descends, and that at the
cathode lighter, and ascends.
Faraday, by passing an electric current upwards through a
strong solution of "Epsom salt" into a layer of distilled
water lying upon it, observed that a layer of magnesia formed
at the upper surface of the lower liquid where it touched the
water, as if the water acted as a cathode. Daniell also sub-
sequently passed an upward current of electricity through
solutions of the nitrates of silver, mercury, and lead, and of
the sulphates of palladium, copper, iron, and magnesium,
into a dilute one of caustic potash, separated from them by
a thin horizontal diaphragm of bladder. Oxygen was deter-
mined to the upper, and the respective metals to the lower
surface of the diaphragm, and coatings of metal, more or less
oxidised, were formed against the latter surface, the oxidation
being more complete the more oxidable the metal ; with the
magnesic solution a coating of oxide alone was formed. More
recently (see Proceedings of the Royal Society, Nos. 212, p. 84,
and 217, 1881, p. 142) I have stated, and shown by suitable
experiments, that "every inequality of composition or of
internal structure of the liquid in the path of the current
must act to some extent as an electrode," and have also shown
that a variety of phenomena take place at such a surface of
mutual contact of two liquids when an electric current passes
through it.
Movements of Liquid Electrodes. As early as the year^
1801 Gerboin observed the peculiar twitching movements of
mercury whilst undergoing electrolysis, and which are now
known to be due to electro-chemical action, and subsequently
Sir H. Davy, Sir J. Herschel, and others investigated them.
These movements are due to the formation and destruction,
attended by contraction and expansion, of films upon the
mercury, and would probably occur with other metallic elec-
trodes whilst in the liquid state in suitable liquids. (See
Gmelin's "Handbook of Chemistry," Vol. I, pp. 381-384.)
Sounds Emitted during- Electrolysis. Whilst investigat-
ing these peculiar movements and the thermic changes of
electrolysis I discovered that in certain liquids a humming
sound is emitted by electrodes of mercury, and that the sur-
face of the mercury is covered with minute waves during the
passage of the current. I also found that the current was
intermittent during these vibrations (see Proceedings of the
Royal Society, 1862). Sounds are not unfrequently emitted
also from other metals whilst depositing, e.g., from antimony.
These are sometimes produced by contraction and cracking of
the metals, at other times by explosion of bubbles of gas.
Deeomposability of Electrolytes. The degrees of facility
with which different electrolytes are decomposed are different.
Faraday has given the following order, the first-named being
the easiest : Solution of potassic iodide, fused chloride of
silver, of zinc, of lead, melted iodide of lead, hydrochloric
acid, dilute sulphuric acid. Smee gives nitric acid, solution
of chloride of gold, nitrate of palladium, chloride of platinum,
argentic nitrate, cupric sulphate, stannic sulphate, dilute
sulphuric acid, solutions of the sulphates of cadmium, zinc,
nickel, iron, and magnesium, and those of salts of the alkalies
generally. Dilute sulphuric acid offers less resistance to elec-
trolysis than one of zinc sulphate, and more than one of
cupric sulphate (Favre, Comptes Rendus, Vol. LXXIII. ; Journal
of 'the Chemical Society, 2nd series, Vol. X., p. 113). I have re-
peatedly observed that hydrochloric acid is decomposed more
readily than water, and water more easily than hydrofluoric
acid, also a solution of selenic acid before one of selenate of
nickel. The readiness of decomposability of an electrolyte
depends upon several conditions, and especially upon the
nature of the electrodes ; thus a solution of potassic cyanide
is readily decomposed when the anode is composed of palla-
dium, silver, or copper, but with difficulty when it is formed
of iron or platinum. A large field of research exists in this
part of the subject.
The decomposability of a liquid is usually increased by rise
of temperature ; it is also influenced by the length of the
liquid portion of the circuit, which is the part in which the
greatest resistance exists to the passage of the current. This
has been shown by Gladstone and "" Tribe, who decomposed
water by immersing in it a pure zinc plate previously coated
clectrolytically with a loose deposit of spongy copper or pla-
tinum, when two plates of those metals connected together
.and immersed at a distance from each other in the liquid
would not decompose it, and have thus shown that " the dis-
sociation of a binary compound may take place at infmitesi-
mally short distances, when it would not take place where the
layer of liquid is enough to offer resistance to the current "
(Proceedings of the Royal Society, Vol. XX., p. 219).
According to Helmholtz, electrolysis of water by a voltaic
current is possible only when the chemical processes in the
battery, taken together, can produce more heat than the
oxygen and hydrogen generated in the voltameter, and
therefore that about 1 J Daniell cells arc required for a con-
tinuous decomposition of water. A single Daniell connected
with platinum electrodes in dilute sulphuric acid produces
only polarisation, no visible decomposition, the voltameter
acting as a condenser of immense capacity (Journal of the
Chemical Society, 2nd series, Vol. XL, p. 463). As a matter of
tact, however, a feeble current passes if the water in the
( 7)
voltameter contains dissolved oxygen, or the platinum plates
occluded hydrogen.
According to- D. Tommasi, "in order that decomposition
may take place when a current passes through several elec-
trolytes, it is necessary that the quantity of heat should be
equal to the sum of the quantities absorbed by each elec-
trolyte, plus the quantity necessary to overcome the total
resistance of the electrolytes. By heat produced by the
battery is meant that transmissible to the circuit. In many
cases in which there is no decomposition when both elec-
trodes are of platinum, decomposition takes place when the
anode consists of some oxidable metal, such as copper or tin."
" Of two compounds, that one is decomposed by preference
which requires the least thermic energy" (Journal of the
Chemical Society, Vol. XLIL, 1882, pp. 134, 353, 789, 1,019,
1,155, and 1,156; see also Favre, "Watt's Dictionary of
Chemistry," Vol. VII., p. 458).
On the subject of "The Limits of Electrolysis" consult
Berthelot (Journal of the Chemical Society, Vol. XLIL, 1882,
pp. 260 and 353).
According to E. Obach, liquid mixtures of metals do not
suffer electrolysis. His experiments were made with alloys of
sodium and mercury, of sodium and potassium, and of tin with
lead. The portions of alloy around the poles after passage of
the current were unaltered in chemical composition (Journal of
the Chemical Society, 1876, Part II., p. 37 ; Chemisches Central
Blatt, 1875, p. 497).
Conduction in Electrolytes without Decomposition.
Whether this takes place or not is an important question, and
after many researches on the subject electricians are even now
not unanimous respecting it. According to Favre's experi-
ments (Comptes llendus Acaddmie des Sciences, Vol. LXXIIL,
p. 1,463), true conduction without electrolysis does occur when
two Smee cells are used to electrolyse dilute sulphuric acid. In
the electrolysis of fused argentic fluoride, also with sheet silver
electrodes, I observed that the liquid conducted the current
with a most extraordinary degree of facility apparently out of
all proportion to the weight of metal deposited. Conclusive
experimental evidence is, however, still much required to settle
the question. With a current of insufficient electromotive
force to decompose an electrolyte, either the electric charges
must accumulate on the electrodes, and the liquid act as a
dielectric, or they must be transmitted by convection or con-
duction.
Circumstances which Affect the Kind of Deposit. Both
the chemical composition and the physical quality of the
substances set free at the electrodes are affected by various
circumstances ; by the composition of the liquid and its degree
of fluidity ; by the strength of the current ; by its density, or
strength in relation to amount of surface of the electrode ; by
temperature, &c., and by various other circumstances.
The products of electrolysis vary also according to the kind
of electrolytic arrangement employed. In the simple im-
mersion one they are mixed with those of voltaic action. In
the case of two metals in two liquids separated by a porous
division, the products of voltaic action and electrolysis are-
largely kept separate, and in the case cf electrolysis in an
undivided cell by means of a separate current, the anode and
cathode products become mixed.
The composition of the liquid is a fundamental condition,,
and variation of it has usually very powerful effects. The
addition of an extra ingredient may cause entirely different
substances to appear at each of the electrodes, or alter both
the quantity and physical condition of the deposits. An
alteration of the degree of fluidity acts similarly, but less
powerfully. Whilst also with one strength or degree of
density of current a single substance only may appear at each
electrode, with a current of greater strength or density
additional bodies not unfrequently are liberated. By either
decreasing the proportion of water mixed with potassic hydrate,,
or increasing the strength or degree of density of the current,
instead of oxygen and hydrogen alone being evolved,
potassium is also set free. A weak current passing through
an ordinary silver-plating liquid containing much free potassic
cyanide deposits hydrogen only ; but by increasing the density
of the current silver is also liberated. It was by obeying
these conditions that Davy isolated potassium, and Bunsen
deposited chromium. Other investigators also succeeded in
obtaining highly oxidable metals in the form of amalgams,,
without the use of powerful current?, by employing as a
cathode mercury, which absorbed the deposits, and thus largely
prevented them from redissolving.
The density of the current affects also the physical proper-
ties of deposited metals. With a weak current and slow action
metals are not unfrequently deposited in a crystalline state,
whilst with a strong one they are thrown down as a soft black
powder. A nearly saturated solution of cupric sulphate,
acidulated with dilute sulphuric acid to a suitable extent,
yields ductile metal when the rate of deposition is about half
an ounce of metal per square foot of cathode surface per hour.
The degree of density of the current not only affects the
physical properties of cations, but also those of anions in some
cases. Thus a stronger current is usually required to liberate
ozone than to set free ordinary oxygen.
Every different metallic solution, and at every different
temperature, must be electrolysed at a particular rate in order
to obtain from it metal in the state of crystal?, reguline metal,
(9)
or black powder. Some solutions will only yield coherent
metal whilst they are hot. If, also, the surface which receives
the deposit varies in degree of smoothness, the physical cha-
racter of the metal is affected. With a viscous solution the
quality of the deposit soon changes, because the exhausted
layer of liquid next the cathode is only very slowly replaced
by solution containing a sufficient proportion of metal.
Different metals whilst depositing exhibit very different
physical properties. Copper depositing upon the bulb of a
thermometer contracts and compresses the glass bulb, and
causes the mercury to rise. This phenomenon has been termed
" eiectro-striction." Grey metallic antimony depositing very
slowly until it has attained l-10th of an inch in thickness
from a solution of tartar-emetic will often crack and curl up in
most fantastic shapes. Nickel when deposited to a thickness
of half an inch is in the form of smooth, round knobs ; copper
has a somewhat similar structure when deposited from certain
liquids, the knobs, however, being usually lough.
Circumstances which Affect the Amount of Electro-Che-
mical Action. First, and essentially, the amount of electro-
chemical effect with each substance is stiictly proportional to
the quantity of current ; double the quantity of current libe-
rates at the cathode double the amount of gas or metal, or
causes double the amount of metal at the anode to dissolve or
gas be evolved. Second, with different substances it varies as
their chemical equivalents, or, in other terms, it varies with
the atomic (or molecular) weight and degree of valency of the
substance. Thus, one atomic weight of any monad element,
say silver (the atomic weight of which is = 108), requires the
same quantity of current as one of any other monad element,
say chlorine (the atomic weight of which is 35 -5) to liberate
it. One atomic weight of any dyad element, say oxygen
( = 16), requires twice the quantity of one of any monad
element; and one of any triad, say antimony ( = 122), or gold
( = 196), requires three times the quantity to make it electro-
lytically dissolve or deposit, and so on, the proportions in all
cases being exactly the same as the ordinary chemical equiva-
lent", and these may be found in any book on general in-
organic chemistry. By passing an electric current through
two liquids in series, one of which yielded by electrolysis pure
copper only, and the other pure antimony only, I found that
the weight of copper deposited was 31 '7 grains, and of anti-
mony 40*6 grains, and this agreed with one atomic weight of
triad antimony or 121-98 parts, being the chemical equivalent
of 1 J atomic weights, or 95-25 parts of dyad copper. In a
series of electrolysis vessels, therefore, containing different
liquids, and electrodes of different metals, the chemical work
done by the current at any one anode or cathode is exactly
equal m value to that done by it at any other of the same
series in tbe same time. In the decomposition of water, there-
fore, by an electric current we obtain two parts by weight of
hydrogen for each 16 parts by weight of oxygen, and in con-
sequence of the specific gravity of the latter gas being sixteen
times greater than that of the former, the relative volumes of
them are as two to one. This exact relation of the quantity of
the current to the amount of its chemical effect with different
substances is known as the law of definite electro-chemical
action, and was discovered by Faraday,
With nearly all, if not all electrolytes, Faraday's law of
definite electro-chemical action is supposed to be true for even
the very smallest currents. The true electro-chemical equiva-
lent of a single substance, however, is only obtained in certain
cases. In some instances a portion of the current passes
through another ingredient of the liquid, and two substances
are deposited simultaneously, and form the equivalent. The
alteration of weight of either electrode during electrolysis is
often not a true measure of current, because the metal is
liable to ordinary chemical action. The true measure is the
total amount of substances liberated, taken before they have
had time to suffer ordinary chemical change.
Influence of Temperature, &c., on Electrolysis. Change
of temperature has a great effect. Both the electric conduc-
tivity and the diffusive power of saline solutions increase by
rise of temperature, and each of these circumstances greatly
promotes electrolysis. Rise of temperature affects also the
relative proportions of current conveyed by the different in-
gredients of a mixed electrolyte ; for instance, I found that
in the electrolysis of an acidified solution of cupric sulphate
with copper electrodes a considerable deficiency of deposited
copper, sometimes amounting to as much as 1G per cent., may
result through employing a hot solution. ("Electrolysis of
Sulphate of Copper," Proceedings of the Birmingham Philo-
sophical Society, Vol. III., p. 75 ; The Electrician, Vol. VIII.,
pp. 271 280). Very few experiments have as yet been made
on the influence of great pressure (see Section 48) or of
magnetism on electrolysis. Remsen, however, found by
depositing copper from a solution of cupric sulphate contained
in a thin vessel of sheet iron, placed upon the pole of a
powerful permanent magnet, that the deposit occurred in a
fairly uniform way on the entire surface of the iron except
at the parts marking the outlines of the poles. These lines
were strongly marked as depressions in the copper. The
action was still more striking when an electro-magnet was
used instead of the permanent one. In a narrow space mark-
ing the outline of the pole there was no deposit. Within
this line it was fairly uniform, but outside of it the copper
( 11 )
aggregated in irregular ridges, running at right angles to the
lines of force, and apparently coinciding with those marking
the equipotential surfaces.
Relations of Electro-Chemical to Ordinary Chemical
Action. Electrolytic changes obey the same law of equiva-
lence of action as ordinary chemical ones, and electro-chemical
action by a separate current may be viewed as ordinary
chemical action taking place in one large and measurable
circuit instead of in a multitude of excessively small and non-
measurable ones ; and conversely, ordinary chemical corrosion
of metals in electrolytes may be viewed as electro-chemical
action taking place in an infinite number of such minute
circuits.
The electrolytic circuits in which electric currents flow
may be of any degree of magnitude, from these small ones
upwards, and such currents, of various degrees of magnitude,
may circulate simultaneously in the same metals and liquid.
Electro-chemical action, therefore, does not necessarily exclude
ordinary chemical change. One large current may flow
through the electrodes and liquid of an electrolytic cell,
whilst "local" action (i.e., ordinary chemical action in patches)
in lesser circuits is taking place upon each of the electrodes,
and also whilst ordinary chemical action is occurring uniformly
upon them.
When an electric current is passed through an electrolyte,
whether attended by corrosion of the anode or deposition of
metal upon the cathode or not, the layers of liquid in contact
with each electrode become changed in chemical composition
and density, and are thus indirectly set in motion by the
influence of the current, and in consequence of this the ordi-
nary chemical action upon them is altered. In some cases
alkali collects around the cathode, and acid around the anode ;
in others the liquid around the former becomes more dilute
and ascends, whilst that around the latter becomes more satu-
rated with salt and descends. In others, again, insoluble gas
is evolved from each electrode, and causes an upward motion
of liquid, and in others the gas dissolves in the liquid and
alters its degree of corrosive power, as well as of specific
gravity ; and in some of these cases, by increasing the density of
the current up to a certain point the ordinary chemical action
of the liquid upon the cathode is diminished until all such
corrosion ceases. This point I have termed " the electrolytic
balance of chemical corrosion," and have investigated it in the
case of silver in an ordinary cyanide plating solution (see Pro-
ceedings of the Birmingham Philosophical Society, Vol. III., pp.
268 305, also an abstract in The Electrician, Vol. X., p. 381).
Many other cases in which ordinary chemical corrosion is
balanced and prevented by electro-chemical action remain to
( 12)
be investigated. In some cases the rate of corrosion of a
cathode is increased during electrolysis, in consequence of the
evolution of hydrogen and consequent motion of the liquid
bringing fresh corrosive particles into contact with it (see
11 Corrosion of Cathodes," Proceedings of the Birmingham Philoso-
phical Society, Vol. III., p. 305 ; The Electrician, Vol. XL,
p. 213).
Electrolytic Balance of Chemical Corrosion. Any mixed
electrolyte with a current passing through it and setting free
one only of its constituents at a corrodible cathode, and the
current then gradually increased until a second cation con-
stituent just begins to be deposited, constitutes an example
of "electrolytic balance." Such a case is that of an acidified
solution of cupric sulphate, with copper electrodes, with the
current increased until metal begins to be deposited ; or that
of the ordinary cyanide of silver plating solution containing
much free potassic cyanide with electrodes of silver, similarly
treated.
Such a silver solution, suffering electrolysis at its "balance
point," forms an excellent illustration of the compensation
and balance of a number of molecular forces, the alteration of
any one of which disturbs the remaining ones. Even a
change of temperature may be included in this statement. It
is a case of balance of powers in which the state of equipoise
depends upon the united and simultaneous action of at least
seven or eight different influences, viz., ordinary chemica)
corrcsion, strength of current, nature of cathode, size ol
cathode, temperature, proportions of water, of argento-potassic
cyanide, free potassic cyanide, and of the soluble salts, &c.,
present in the form of impurities. Additional causes, 01
conditions, might also be introduced, which by their pre-
sence would probably affect the state of balance, such, for
instance, as by dissolving in the liquid various salts or other
substances.
Several of these causes or conditions may be modified so
as to alter the balance either in one or the opposite manner.
Thus, increased chemical corrosive power, a larger cathode,,
more free potassic cyanide, less argentic cyanide, or less
strength of current alter the balance in one direction, whilst
their opposites alter it in the contrary one.
Such experiments also show that the various conditions of
the state of balance may either assist or counteract each
other; that an increase of current is equivalent to a decrease
of argentic cyanide, if the one is increased the other must
be decreased in order to maintain the state of the balance ;
that an addition to the amount of free potassic cyanide,
by diminishing resistance, is equivalent to an increase of
current; that a decrease of cathode surface necessitates
(13)
either a decrease of argentic cyanide or of current; that a
rise of temperature is balanced by an increase of current,
and so on.
All these influences have numerical values. In the experi-
ments referred to it is shown that a rise of temperature of the
liquid of 60 Fahrenheit degrees, i.e., from 60 to 120 F., is
balanced by an increased strength of current from '002306 to
003282, or -000976 ampere.
The arrangement and use of a depositing solution in such a
manner constitutes a method of detecting the molecular
influences of substances dissolved in electrolytes, and of deter-
mining to a certain extent their kind and amount of influences
by their effect and degree of power in altering the " balance
point " either in one direction or the opposite. It was found
that the mere presence and admixture in solution of even a
small quantity of argento-potassic cyanide in the above liquid
altered the molecular arrangement of the free potassic cyanide
in such a way as to diminish its power of alone transmitting
the current into a silver cathode, and increased the tendency
of the current to pass into the cathode partly by means of the
double salt.
The phenomena of the "balance point" constitute also an
interesting example of molecular equilibrium, in which the
" balance point " may be compared to a ball suspended by an
elastic cord and having attached to it a number of other
similar cords in a state of tension, each drawing it in a different
direction. In such a case an alteration of the degree of strain
of any one of the cords changes that of all the others, and
alters the position of the ball.
Secondary Effects of Electrolysis. In very many cases
the new substances actually observed at the electrodes are
not those set free by the current, but are products or results
of the action of those substances upon the liquid or upon the
electrodes. Thus, when potassium is deposited from a solu-
tion of one of its salts into a cathode of mercury, the liquid
in contact with the mercury becomes alkaline ; when iodine is
set free from the cathode in a solution of iodic acid, it is due
to the deoxidising action upon the iodic acid of the hydrogen
liberated there by the electrolysis of the water or of the iodic
acid, and when it is set free at the anode during electrolysis of
a solution of hydriodic acid it may be viewed as a direct result
of the current or as a secondary result of liberated oxygen.
The peroxide of silver formed at an anode of platinum in a
solution of argentic nitrate may be viewed as a secondary pro-
duct due to the action of the liberated oxygen or ozone upon
the silver of the liquid. In many cases it is difficult to deter-
mine whether a liberated substance is due to primary or to
secondary action.
( 14)
Faraday advanced the view that " only those compounds of
the first order are directly decomposable by the electric current
which contain one atom of one of their elements for each atom
of the other ; for instance, compounds containing one atom of
hydrogen or metal with one atom of oxygen, iodine, bromine,
chlorine, fluorine, or cyanogen, whilst boracic anhydride (B0 3 ),
sulphurous anhydride (S0. 2 ), sulphuric .anhydride (SO 3 ), iodide
of sulphur, the chlorides" of phosphorus (PC1 3 and PCl r( ),
chloride of sulphur (S 2 C1), chloride of carbon (C 4 C1 6 ), tetra-
chloride of tin (SnCl 4 ), terchloride of arsenic (AsCL), penta-
chloride of antimony (SbCJ-), are non-conductors of electricity,
and incapable of electrolysis." I have observed that the
decomposability of a salt depends upon the kind of liquid in
which it is dissolved ; e.g., the iodide and bromide of antimony,
both of which conduct and are decomposed when dissolved In
acidulated water, do not conduct and are not decomposed
when dissolved in carbonic bisulphide.
Insoluble Coatings on Anodes. In many cases of electro-
lysis of aqueous solutions, the anode does not dissolve, but
becomes coated with an oxide, chloride, fluoride, cyanide,
sulphate, or other insoluble salt, usually by chemical union of
the metal with an ingredient of the liquid. In this way silver
in dilute hydrochloric acid becomes coated with argentic
chloride ; in a solution of argento-cyanide of potassium it
becomes covered with argentic cyanide, lead in dilute hydro-
fluoric acid becomes coated with fluoride, and so on. In some
cases the insoluble coating occurs not by corrosion of the
anode, but by the oxygen evolved by electrolysis of the water
acting upon the ingredients of the solution; in this way
various peroxides are formed. The formation of peroxides
occurs upon platinum anodes in solutions of the nitrates of
bismuth, silver, and lead ; in certain alkaline solutions of lead,
nickel, and cobalt, and in those of nitrate and acetate of
manganese, and when the films which are thus formed
are exceedingly thin their colours are in some cases very
magnificent.
Electrolytic Alloys. In many cases when metals are de-
posited upon metals, the two substances form alloys ; grey
antimony deposited upon mercury from a solution of tartar
emetic alloys readily, but the black explosive variety does
not. Tellurium deposited from a solution of its chloride upon
platinum also forms an alloy. Boron, silicon, and lithium,
when deposited from certain fused compounds upon a surface
of platinum, also alloy with it. Hydrogen deposited upon
palladium, or upon certain other metals, iron in particular, is
absorbed, and imparts to the metal peculiar properties. In
some cases the absorption of the deposited substance con-
tinues after deposition has ceased ; this is only visible in cases
( 15 )
where the deposited coating is extremely thin. A thin film
of deposited copper is absorbed by zinc.
Purity of Electrolytic Deposits. Not only do the de-
posited substances sometimes alloy with or penetrate into
the mass of the cathode, but in some cases during the act of
deposition they combine with some of the elements of the
electrolyte, and are thereby altered in property. In this way
antimony which has been rapidly deposited from a strongly
acidified solution of its oxide in hydrochloric acid contains
several per cent, of the salt derived from the liquid, and
possesses the very remarkable property that, if broken, or
even scratched, it suddenly rises in temperature about six
hundred Fahrenheit degrees ; it also has the appearance of
highly burnished steel, very widely different from the colour
and appearance of the pure grey metal very slowly deposited
from a feebly acidified solution of tartar emetic in dilute
hydrochloric acid. This black antimony gradually loses its
latent heat, explosive power, and brilliant appearance, in
the course of one or two years, the period varying according
to the thickness of the deposit.
It, is only in certain cases and in the presence of a collec-
tion of suitable fortuitous conditions that a deposited sub-
stance is extremely pure ; substances very easily deposited,
such as hydrogen and copper, are usually so chiefly because it
requires a stronger power to deposit most other bodies, also
because in some cases the other easily deposited metals are
precipitated as insoluble salts by ordinary chemical action.
Thus lead in an acidified solution of sulphate of copper is pre-
cipitated as sulphate ; similarly silver is precipitated in a solu-
tion containing a dissolved chloride. All deposited substances
are, of course, more likely to be pure the greater the degree
of purity of the liquid.
Divided Electrolysis. When an impure liquid or a mix-
ture of solutions is electrolysed, either a single substance
alone may appear at the anode or cathode, or several may
be simultaneously liberated. With a feeble current and large
electrodes one substance alone may appear at either electrode,
but by either increasing the strength of the current or
diminishing the size of the electrodes, a second, or even a
third substance may be liberated, the current appearing to
divide its action amongst the various compounds present. The
least electro-positive cation is usually liberated first, and the
more positive ones subsequently as the current strength is in-
creased. In all cases weaker affinities appear to be overcome
first ; but this is only a superficial explanation, the true one
being much less simple. By employing proportions of the
substances, larger as their electro-positive property in the
particular liquid is greater, several may be simultaneously
(1C)
deposited or the more positive ones may be deposited even in
larger amount than the less positive ones, as for instance
potassium from moist potassic hydrate. It is by obeying these
and other conditions that alloys and mixtures of substances
are usually set free at the electrodes. The order of degree of
electro-positive state of the metals desired to be deposited may
in most cases be ascertained by connecting the metals in pairs
with a galvanometer, immersing their free ends in the liquid,
and observing the direction of deflection of the needles.
In electrolysing a mixture of the sulphates of zinc, cadmium,
and copper, Favre succeeded, by altering the conditions of the
experiments, in obtaining at will either one, two, or all the
three metals simultaneously ; and states that the results of the
operation vary, 1st, with the voltaic energy of the battery ;
2nd, with the electrolytic resistance of the salts ; 3rd, with
the relative quantity of each salt ; and 4th, with the greater
or less rapidity of the electrolysis, which can be regulated.
He concludes that by varying these conditions we are enabled
to withdraw from a mixture of salts the different metals in
succession, and thus proposes an electro-chemical analysis
(Ccmptes fiendus, Vol. LXXIII. ; Journal Chemical Society,
2nd series, Vol. X., p. 113). This proposal, however, is not
a new one.
Polarisation of Electrodes. In consequence of the altera-
tion both of the chemical composition of the surface of the
anode and of that of the cathode, and also of that of the
layer of liquid in contact with each of the electrodes by elec-
trolytic action, the electric state of each of these surfaces is
continually liable to change ; or, in other words, the surfaces
become polarised. And as the substances set free at the anode
are usually electro-negative, and those at the cathode are
usually electro-positive, the electric states produced by polari-
sation are opposite in kind to the original one?, and tend to
produce an electric current in an opposite direction to the
previous one, and therefore weaken that current. According
to M'Gregor (Nature, July 19, 1883, p. 283), the degree of
polarisation of electrodes is independent of their degree of
difference of potential. By passing an undivided current by
means of four similar platinum sheet electrodes through two
cells containing equal sections but unequal lengths of dilute
sulphuric acid (the current being therefore of equal density in
each and the electrodes of the two vessels of unequal poten-
tial), he found that the variation by lapse of time of the
electromotive forces of the two cells after cessation of the
polarising current was similar.
Unequal Electric Action at Electrodes. By the electro-
lysis of a metallic electrolyte by means of vertical corrodible
-electrodes, the liquid around the anode usually becomes more
saturated with metallic salt, and being heavier descends,
whilst that around the cathode becomes deprived of metal,
acquires less specific gravity, ascends, and spreads itself over
the surface. In consequence of these variations in specific
gravity of the upper and lower parts of the electrolyte, the
direction of the current in it is gradually affected. At first,
whilst the liquid is uniform in density and composition
throughout, the whole of the current is perfectly horizontal
in direction, and equal amounts of it pass through equal
sections of the liquid ; but, if the current is sufficiently strong,
after a while it passes unequally, and the bulk of it travels in
an oblique direction from the upper part of the anode to the
lower part of the cathode. In consequence of this, the greatest
amount of electrolytic effect is at those parts of the electrodes,
and thus in some cases the upper part of the anode is rapidly
corroded, whilst the lower part of the cathode receives a rapid
deposit. If, however, the current is very feeble, the liquid is
kept uniform in composition by means of diffusion as fast as it
is rendered non-homogeneous by electrolysis ; if also the liquid
is very viscous and diffusion difficult, these phenomena are
more slowly produced. These changes in composition of the
upper and lower parts of the liquid also give rise to local cur-
rents, which leave the upper part of each electrode and re-enter
at its lower portion, and produce the usual electrolytic effects,
With the electrodes horizontal, and the cathode below the
anode, the above inequalities of electrolytic action do not,
occur.
In some cases, apparently in consequence of a very thin
layer of corrosive liquid collecting upon the surface of the.
electrolyte by long-continued rapid electrolysis, the anode is
gradually cut off at that level and falls to the bottom ; in
other cases, partly in consequence of evaporation, of oxidation
of moist metallic surfaces by the air, and of capillary action,
the cathode is corroded in numerous short vertical grooves at
the surface line of the liquid, and a narrow line of metallic
deposit gradually forms above the surface of the liquid, and
follows the outline of the narrow film of liquid which has risen
by capillary action. A probably correct explanation of the
formation of this deposit is that the capillary film of liquid
becomes much less corrosive and more saturated with the
metal by chemical action than the bulk of the liquid beneath.
The piece of metal is therefore in contact with two liquids of
different chemical composition, and a voltaic element is thereby
formed and generates a current, the positive electricity of
which proceeds from the portion of surface of metal which
is in the upper and nearest part of the bulk of the solution
into that solution, thence to the capillary film, and into the
narrow surface of metal in immediate contact with it, and thus
corrodes the metal just below the surface of the liquid, and
(18)
deposits the metal in the capillary film. This phenomenon is
seen in alkaline liquids as well as in acid ones ; for instance,
with silver in a solution of potassic cyanide.
The corrosive effect attending this capillary action differs
somewhat with different metals and liquids. With metallic
tin, in particular, in dilute hydrochloric acid, in some experi-
ments of mine, grooves about '5mm. deep were corroded in its
surface and extended in a vertical direction to a distance of
nearly 7mm. ahove the level of the liquid. The grooves were
crooked, and had branches like those of a tree, and those upon
the cathode were longer and deeper than those on a similar
sheet of metal in a separate portion of the same liquid not
under electrolysis.
Dependence of Electrolysis upon Liquid Diffusion. This
is a branch of the subject which has hitherto been but little
examined, and much remains to be discovered in it. Many of
the phenomena of electrolysis are, no doubt, essentially related
to the power of liquid diffusion. An extremely viscous liquid
admits of but slow electrolysis. Long has discovered (Phil.
Mag., 1880, Vol. IX., p. 425) that in almost every case the
best conducting saline electrolytes are solutions of those salts
which have the fastest rate of diffusion, and those are usually
the salts which have the largest molecular volume, and which
,-also absorb most heat in dissolving. He also arrives at the
conclusion that " the rate of diffusion of a salt is proportional
to the sum of the velocities with which its component atoms
move during electrolysis."
Electrolytic Diffusion of Liquids. I have experimentally
investigated this converse part of the subject (see Proceedings
of Royal Society, No. 203, 1880, p. 322, and No. 212, 1881,
pp. 56 84), and have shown that an electric current will
cause a liquid to diffuse, and I discovered that when such a
current was passed up or down through the surfaces of mutual
contact of certain aqueous solutions of different specific
gravities lying upon each other in well-defined layers, the
bounding surfaces of contact of the two liquids became indefi-
nite where the current passed downwards from the lighter to
the heavier solution, and became more sharply defined where
it passed upwards from the heavier into the lighter one ; and
that, on reversing the current several times in succession, after
suitable intervals of time, these effects were reversed with
each such change of direction ; also, in various cases in which
the contiguous boundary films of the two liquids had become
mixed, and the line of separation indefinite, the liquids sepa-
rated by the influence of the upward electric current, and the
line of separation became as perfect as that between strata of
oil and water lying upon each other. I also observed, 1st, the
production of definite lines, not only where the current passed
( 19)
from the heavier into the lighter solution, but also (in certain
cases) at the surface where it passed from the lighter to the
heavier one. 2nd. The production in some cases of two or
three separate lines at the former situation, and less frequently
also at the latter one. And, 3rd, an apparent movement of
the mass of the heavier solution, usually in the direction of
the electric current, but in certain exceptional cases in the
reverse direction. By further experiment (see Proceedings of
the fioyal Society, No. 217, 1881, p. 141) I ascertained that, 1st,
in certain cases the upper and lighter liquid diffused down-
wards continuously through the meniscus, or surface of separa-
tion of the two liquids, during the passage of an upward
electric current ; and, 2nd, that during the continuance of the
current either no manifest expansion of the upper liquid
occurred, and that equal volumes of liquid diffused in two
opposite directions through the meniscus, or that any expan-
sion of the upper liquid was compensated by downward
diffusion of an equal bulk of that liquid ; or that the united
volumes of metal deposited from the upper liquid, and of the
acid element from which it had been separated by electrolysis,
were greater than before such separation, and that this was
compensated by the volume of liquid diffused downwards
.through the meniscus. In these latter experiments the
meniscus retained its position during the passage of the
current, thereby proving that the actual bulk of the upper
liquid remained the same whilst diffusion of a portion of that
liquid took place downwards through the meniscus.
Transport of Ions. Hittorf and G. Wiedemann found that
usually the velocity of transport in electrolysis of anion and
cation are different, and F. Kohlrausch discovered that in
dilute solutions of salts, acids, and alkalies every ion under
the influence of currents of equal density moves with its own
particular velocity, independently of others moving at the
same time in the same or opposite direction. The order of
velocity of cations, the first named being the fastest, was
hydrogen, potassium, ammonium, silver, sodium, barium,
copper, strontium, calcium, magnesium, zinc, lithium; and
of anions was hydroxyl, iodine, bromine, cyanogen, chlorine,
N0 3 , C10 3 , and the halogen of acetic acid.
Relations of Electrolysis to Heat. In consequence of
chemical action and of the passage of an electric current
from one substance to another, changes of temperature occur
at each electrode, and at each junction of two different
liquids. These changes are different in every different case,
and have been but little investigated. With an anode of
copper in an acidulated solution of its sulphate, heat is
evolved by the oxidation of the metal ; but with one of
platinum in dilute sulphuric acid, heat is absorbed, and
c 2
(20)
oxygen is reduced to the elementary state. At the cathode-,
in the former liquid, copper is liberated and heat absorbed ;
but with a platinum cathode in nitric acid, heat is set free by
oxidation of the deposited hydrogen.
According to Favre (Comptes Rendus, Vol. LXXIIL, pp.
1,0361,085, 1,1861,262), although in certain cases the
metal dissolved at the anode is all reproduced at the cathode,
heat is liberated which is not transmissible to the circuit.
The oxides and salts of the alkali metals, when subjected to
electrolysis, are decomposed, and give up their metal, which
metal being directly oxidised at the expense of the water, sets
free a quantity of heat which reinforces the voltaic energy of
the battery. The secondary reactions which accompany elec-
trolysis and produce heat not transmissible to the circuit
always tend to strengthen the energy of the battery when-
ever the current is weak and when the electrolysis offers
great resistance. Such secondary reactions are, for example,
produced by the hydrogen and the oxygen set free during
electrolysis, the first being burned, the second oxidising any
oxidable substance present (Journal of the Chemical Society,
2nd series, Vol. X., pp. 110113).
In addition to changes of temperature produced by electro-
chemical and chemical actions in the electrolyte, heat is
evolved by conduction-resistance in the mass of the liquid ;
and I have noticed that if two large masses of the same, or of
two different electrolytes, are united by an open short glass
tube of the shape of an hour-glass, and of small diameter, by
employing a sufficiently strong current the liquid in the
narrow part of the connecting tube may be caused to boil
("Influence of Voltaic Currents on Diffusion of Liquids/'
Proceedings of the Royal Society, 1881, No. 213, pp. 7682).
Gladstone and Tribe have shown by experiment that if a
strip of metal is immersed at its two ends in a salt of the
same metal in a state of fusion, but of unequal temperature
at the two parts where the metal dips into it, the hotter end
of the metal dissolves, and the less heated part receives a
metallic deposit. Copper in fused cupric chloride is an
example (Journal Chemical Society, Vol. XL., 1881, p. 868).
Theories of Electro-Chemical Action. Various theories
have from time to time been proposed to account for the
leading phenomena of electrolysis, but none of them have as
yet been very clear or satisfactory. One of the best is that
propounded by Faraday. He considers that electrolysis
resulted from a peculiar corpuscu 7 ar action developed in the
direction of the current ; and that it proceeded from a force
which was either added to the affinity of the bodies present,
or determined the direction of that force. That the electro-
lyte was a mass of acting particles, of which all that were in
(21 )
the course of the current contributed to the teiminal action,
and in consequence of the affinity between the elements being
weakened, or partially neutralised by the current parallel to
its own course in one direction, and strengthened and assisted
in the other, the combined particles acquired a tendency to
move in different directions. The particles of one element,
a, cannot travel from one pole to the other, unless they meet
with particles of an opposed substance, 6, ready to move in
the opposite direction. For in consequence of their increased
affinity for these particles, and the diminution of their affinity
for those which they have left behind, they are continually
driven forward.
Any tolerably complete theory of electrolysis of a funda-
mental character must, however, be a mechanical one, based
upon the assumption of molecular motion, and expressible
in mathematical and geometrical terms. Whilst, also, the
theory must represent the kind of molecular motion which
constitutes an electric current, it must also be consistent
with the numerous and varied phenomena attending electro-
chemical action. And as the essential kinds of molecular
change which occur at the electrodes are probably more or
less modified in every different case, a complete theory must
admit of varied application. Clausius considers that the atoms
or groups of atoms forming a molecule of an electrolyte
revolve around one another, similarly to planets, and are
sometimes nearer to and sometimes farther from each other
("Poggendorff's Annalen," CLVL, pp. 618 to 626). Favre
states (Comptes Rendus, Vol. LXXIIL, p. 971) that in each
voltaic couple the molecules are electrolysed successively, and
that when the absolute number of vibrations which correspond
to a given intensity of the current have been determined the
absolute iveight of the chemical molecules will be known (Journal
Chemical Society, 2nd series, Vol. X., p. 25).
The immediate or primary electrolytic changes are evi-
dently a result of molecular energy transmitted along the
wires from the source of the current; and the energy so
transmitted is substantially the same in its chief properties
and electrolytic effects, whether it proceeds from a voltaic
battery, a thermopile, or a dynamo electric machine. Any
theory, therefore, which explains electrolysis must also be
consistent with the fact that in the act of electrolysis the
homogeneous electric energy is converted into potential mole-
cular energy as varied in kind as the properties of the liberated
elements. It must also explain why the same element may
in certain cases be an anion in one combination and a cation in
.another.
Distinction between Voltaic and Electrolytic Action.
These two actions are almost entirely the converse of each
(22 )
other ; the former is a consumer, and the latter a producer of
potential molecular energy. In voltaic action substances are
burned, in electrolytic they are unburned. In a voltaic cell
potential or stored-up energy of elementary substances is con-
verted into electric current ; in an electrolysis vessel current
is converted into stored-up potential energy in the elementary
substances liberated at the poles.
Intimate Connection of Voltaic and Electrolytic Action.
As in nearly every voltaic circuit the current produced at the
positive surface decomposes the liquid at the negative one, and
in nearly every electrolytic circuit voltaic currents are pro-
duced by difference of chemical composition of the liquids in
contact with the two electrodes, nearly every voltaic circuit is
partly electrolytic, and nearly every electrolytic circuit is
partly voltaic.
According to these views, voltaic action is chemico-electric,
and a case of chemical union in all cases ; and true electrolytic
action is always a case of electro-chemical separation, some*
times accompanied by chemical union at the electrodes.
The various phenomena of electrolysis are produced not
only by electric currents proceeding from an external source,
but also by those produced in the electrolyte itself ; and also
not only by currents generated and flowing in circuits of
measurable magnitude in that liquid, but also by others in
circuits so small that they cannot be measured.
In the case of an ordinary voltaic cell or electrolytic
vessel, the positive and negative surfaces are sufficiently far
asunder to enable us to perceive the action at each ; but in
those of "local action" and minute circuits, such as those
in cases of deposition by " simple immersion," or the chemical
substitution of one metal for another, as when iron becomes
coated with copper by simply immersing it in a solution
of cupric sulphate, the positive and negative surfaces of
each circuit are so excessively small, so exceedingly near
together, and the circuits are so numerous that they cannot be
separately observed, and the entire immersed surface of the
metal is covered with inseparable voltaic and electrolytic actions.
The substances set free by electrolysis do not always
appear; the instant they are liberated they are subject to
ordinary chemical action by contact with the liquid, the
electrodes, and the atmosphere. Thus, when potassium is
set free at the cathode from a solution of any of its salts, it
is instantly oxidised into potash ; or oxygen set free at a
copper anode instantly oxidises the copper. Other relations
of electrolytic to ordinary chemical action have already been
described.
These facts show the intimate connection of chemical,
electro- chemical, and voltaic phenomena; that the study of
(23 )
electro-chemistry requires considerable knowledge of voltaic
electricity ; and that the modes of electrolysis require to be
classified according to the magnitude of the electric circuits
and the degree of complexity of the voltaic and electrolytic
combinations employed. Neither voltaic action nor electrolysis
can be successfully studied without also a previous knowledge
of general chemistry. As the subject of these articles is
electrolysis and not voltaic action, the latter will only be ex-
plained so far as is necessary to elucidate the former.
Modes of Generation of Voltaic Currents. A voltaic
current may arise First, from the contact of two metals with
one liquid, e.g., zinc and copper in dilute sulphuric acid;
second, from the contact of one metal with two liquids, e.g. t
two pieces of silver, one in a solution of potassic cyanide, and
the other in argento-cyanide of potassium, the two liquids
touching each other through an intervening porous partition,
or by lying upon each other; or third, from the contact of two
metals with two liquids so arranged, e.g., zinc in dilute
sulphuric acid, and copper in a solution of cupric sulphate.
The strength of current thus obtained is usually the greater
the more wide the difference in the chemical properties of the
metals and liquids employed, and is commonly the greatest
with the combinations of two metals with two liquids.
Source of the Current. Theory of Voltaic Action. Two
rival theories of the source of the current have long been
entertained First, that of Volta, that the current is due to
contact of dissimilar conductors of electricity; and second,
that of Faraday and other English investigators, that it is due
to chemical action. Neither of these views, however, is com-
pletely satisfactory, or has been universally accepted.
If, however, we adopt a theory that the molecules of sub-
stances (those of chemically active bodies in particular) are in a,
state of ceaseless motion (that of frictonless bodies in a friction-
less medium, the universal ether) until they chemically unite, an
efficient cause of the current (and of chemical action) becomes
at once exceedingly clear.
According to this view, which I may term the Ceaseless
Molecular Motion Theory of voltaic and chemical action, neither
contact nor chemical action is the real dynamic cause of the
current, but the true cause is the potential molecular energy
of the corroded metal, and of the corroding element of the
liquid with which it subsequently unites, and chemical corro-
sion is only the process or mode by which the molecular motions
of those substances are transformed into heat and current.
Both the heat and electric current produced during the
chemical corrosion of metals by electrolytes are recognised
modes of motion, or forms of active molecular energy, and as
motion or energy cannot be created, but can only result from
(24)
the expenditure of some other form of motion, these move-
ments are derived from the original metal and liquid, and the
corroded metal and liquid employed have, after the action, lost
to a greater or less extent their power of further producing
heat or current.
According to this view, also, contact is only a static condition
which enables the molecular motions of the one substance to
modify those of the other, and thus produce static electric
polarity; and this, if sufficiently strong, produces corrosion
and the new modes of motion, namely, heat and current.
Electrical Theory of Chemistry. This theory (attributed
to Berzelius) assumes that the chemical union of any two sub-
stances is an electrical act; i.e., that during contact, previous
to union, the one substance is relatively positive, and the other
relatively negative, and that the act of union is a consequence
of these states ; also that during the act of union the two
electric states neutralise each other and produce heat and
current.
In accordance with this theory, and with the voltaic series
of metals, the various elementary substances have been
arranged in the following order, the most strongly electro-
positive substance being placed first, and the most negative
one last: Caesium, rubidium, potassium, sodium, lithium,
barium, strontium, calcium, magnesium, aluminium, zinc,
cadmium, iron, cobalt, nickel, lead, tin, copper, mercury,
silver, palladium, gold, indium, rhodium, platinum, hydrogen,
osmium, antimony, tellurium, arsenic, silicon, carbon, phos-
phorus, selenium, iodine, bromine, chlorine, nitrogen, sulphur,
fluorine, oxygen.
The electrical theory of chemical action may be reasonably
-extended from that of metals and electrolytes to that of all
non-conducting elements in non-conducting liquids, because
resistance to conduction is only of degree, and not infinite.
If, therefore, the electric polarity produced by the molecular
motions of bodies is sufficiently strong, and the electrical
circuits sufficiently small, chemical union and electrolysis in
non-conductors must occur.
The deposition of copper and silver from aqueous solutions
of their salts by immersing in them a piece of ordinary
phosphorus, are good examples of electrolysis produced by a
non-conducting element in conducting solutions, and the
separation of hydrogen from pure water by contact of a zinc-
platinum couple is an instance of electrolysis by conducting
bodies in a non-conducting liquid. And the chemical decom-
position of non-conducting liquids by non-conducting elements
may be regarded as only an extension of the same kind of action.
Voltaic Series. The degree of power of generating a
voltaic current differs with every different metal and liquid.
( 23 )
The relative power of two metals is usually ascertained by
connecting them with the ends of a galvanometer coil, then
immersing the free ends of the metals simultaneously in the
particular liquid, and observing the direction of deflection of
the galvanometer needles. The strongest acting metal is
electro-positive.
In this way numerous tables of what are termed voltaic
series of metals in various electrolytes have been obtained,
which differ somewhat with every different liquid, and also
with the same liquid of different temperatures or strengths,
but are usually approximately in the above order. For the
order in any particular liquid the reader is referred to text
books on electro-metallurgy, and t<? special researches on the
subject. Extensive series may be found in " Gmelin's Hand-
book of Chemistry," Vol. I., p. 397 ; also Proc. Roy Soc., No.
200, 1879, pp. 3849; and in 'Electro-Metallurgy," Long-
man's Text Books of Science.
The above series are only those obtained by immersing two
different metals in one liquid; others are obtained by im-
mersing two pieces of the same metal in two different liquids
separated by a porous partition ; and more complex ones
might also be formed by immersing two metals in two liquids
thus separated ; and series may also be obtained by the em-
ployment of fused electrolytes in place of the usual aqueous
solutions.
Voltaic Batteries. Voltaic elements are simply combina-
tions selected from series arrived at in the above manner,
those being selected which include the best combination of
desired qualities, such as strength of current, cheapness of
metal and liquid, manageability, freedom from offensive
fumes, &c. A strong element can only be obtained by select-
ing metals which are far asunder in the " series." The
strongest are those formed of two metals and two liquids.
The varieties of batteries are very numerous, and a complete
description of them would fill a volume.
Voltaic Currents. The continuous union of the two
electricities, or electric states of positively and negatively
charged substances, through a conductor, constitutes an elec-
tric current ; and the chief circumstances to be considered in
connection with such currents are polarity, potential, electro-
motive force, quantity, strength, and density of current, con-
duction, resistance, polarisation, &c.
Polarity, Potential, Electromotive Force, &e. Assuming
the Ceaseless Molecular Motion Theory of voltaic (and
chemical) action to be the correct one, we may consider the
pre-existing molecular vibrations of the metals to be the cause
of volta-static polarity and all its consequences ; that when
two different metals are brought into mutual contact, the
( 26 )
molecular motions of the two metals act upon each other ; and
the composition of forces causes the one metal to become
positive and the other negative ; also that, when a metal is
brought into contact with an electrolyte, similar effects of
polarity occur.
Previously, therefore, to the completion of the circuit and
formation of a current, the two metals, by contact with an
electrolyte, become charged with the two kinds of electricity
in a statical condition, and are in a state of electric potential
or pressure, capable of doing electric work by their subse-
quent discharge. This difference of electric potential pro-
duces electric flow, like a difference of pressure of water pro-
duces a flow of that liquid. The electric charges of the
metals are in a state of tension tending to escape, and may be
detected by means of an electroscope or measured by an
electrometer ; the degree of tension is, however, exceedingly
minute. The charged state also produces induction, which
acts from molecule to molecule during discharge, and precedes
current.
Electromotive force, or the power which moves, or tends to
move, electricity from one place to another, varies with every
different voltaic couple, and with the same couple at every
different temperature ; and these differences may be detected
by opposing the two couples to be compared, in single series
in circuit, with their terminals connected to those of a galvano-
meter ; the current from the strongest then produces a deflec-
tion of the needles. In a voltaic series, the metals are arranged
in the order of their relative degrees of electromotive force.
The degree of electromotive force of a couple depends con-
siderably upon the degree of difference of strength of chemical
affinity of the two metals for the electro-negative elements of
the liquid ; and the farther asunder the metals are in the
chemico-electric or volta tension series, the greater usually is
the electromotive force of the current they produce. All
other circumstances being alike, the most rapidly corroded
metal, used with the least corroded one, usually gives the
current of greatest electromotive force.
The measurement of the degree of electromotive force of a
voltaic cell is usually made by comparing it with that of some
convenient and steady source of current, such as that of a
Daniell or a Clark cell. The unit of electromotive force (E) is
termed a volt, that of a Daniell cell is = 1 -078 volt, and that
of a Clark =1-457 volt. For measuring feeble electromotive
forces I have devised a convenient form of thermopile, con-
sisting of about 300 pairs of iron and German silver wires,
and have employed it in making a great number of measure-
ments, not much exceeding that of one Daniell. It is capable of
measuring differences of ^-y^^-th of a volt. (See Proceedings
of the Birm. Phil. Soc., Vol. IV., Part 1.)
( 27 )
Resistance. Every conductor of electricity, no matter how
good it may be, is an obstacle to tlie passage of a current.
Electrolytes offer great resistance, especially with anodes com-
posed of a metal which does not readily dissolve in them.
Perfectly pure water with platinum electrodes hardly trans-
mits any current from, a single voltaic cell. The degree of
resistance of a saturated solution of sulphate of copper at
48 F. and this is a comparatively good conducting elec-
trolyte is nearly 17 million times that of a copper wire of
equal length and section at 32 F. Tables of the con-
duction resistance of various liquids are contained in most
works on voltaic electricity.
According to Quincke ("Pogg. Annalen," Vol. CXLIV.,
pp. 1-33, 161-190), as long as the density of the current in
the liquid is too small to overcome the chemical affinity the
liquid will behave as an insulator, but it may become con-
ducting by an increase of that density. Liquids conduct,
according to Ohm's law, the same as solids (Journal Chemical
Society, 2nd series, Vol. X., p. 208).
The total resistance in an electrolytic circuit is usually
divided into internal, or that in the battery, and external, or
that in the remainder of the circuit ; there is resistance in the
battery itself, in the liquid, and especially at the surface of
the negative plate, if hydrogen is evolved there.
The ordinary unit of resistance (R) is termed an ohm, and
is that offered at C. by 1*0486 metre length of mercury of
1 square millimetre section. The amount of resistance in a
wire, A, is conveniently measured by dividing the current
from a very small Daniell cell, so that one portion shall pass
through A and one wire, B, of a differential galvanometer, and
the other portion through another wire of known resistance, C,
and the other wire, D, of the galvanometer in the opposite
direction to that through B, and altering the length of A until
the needles of the instrument stay at zero. The resistance
in A and C is then equal. The measurement of resistance of
an electrolyte is much more difficult on account of the varying
polarisation of the plates, but may be effected in a somewhat
similar manner by making two measurements by means of a
very feeble current after the polarisation has become steady
one when the electrodes are near together, and the other when
they are far asunder, using in each case electrodes as large as
the transverse section of the liquid, and in certain cases of the
same metal as that of the salt of the electrolyte in order to
diminish polarisation. The difference of resistance of the two
measurements is the amount of resistance of the difference of
length of liquid in the two cases.
Strength of Current The strength is the amount which
flows through any transverse section of the circuit in a given
period of time, and the amount flowing at any given instant
is the same in every such section of the circuit, whether
that section be large or small ; the unit of time employed is
one second. It varies directly as the electromotive force, and
inversely as the total resistance in the circuit (Ohm's law).
A given voltaic cell can only yield a certain maximum
strength of current, and any conductor introduced into the
circuit diminishes that amount. The greater the electromotive
force of a current, the less is it diminished by increase of
external resistance ; such a current is said to possess " great
intensity." If the external resistance is very small, an increase
of electromotive force of the battery adds very little to the
strength of the current ; but if it is large, the opposite effect
takes place. The difference of effect produced by means of a
current from a single cell, and one from many, does not arise
from any difference in the nature of the current in the two
cases, but from the difference of proportion of internal to
external resistance. No difference has hitherto been proved
to exist in any two currents of equal strength.
The unit of strength of current (I) is termed an ampere,
and is the strength produced by an electromotive force of
1 volt in a circuit having a resistance of 1 ohm. The strength
(or quantity per second) of a current may be measured by
passing the current during a known period of time, either by
means of platinum electrodes through dilute sulphuric acid
in a voltameter, and measuring the evolved hydrogen, or by
means of silver electrodes through a solution of argento-
cyanide of potassium, containing the minimum practicable
amount of free potassic cyanide, and weighing the deposited
silver. The latter method gives a little deficiency, owing to
a small amount of the current passing through the free
cyanide. Each '000162 grain of hydrogen or '017343 grain
of silver deposited per second equals 1 ampere. Additional
methods of measurement are usually described in text books
on voltaic electricity.
Unit of Quantity of Current. Whilst the degree of inten-
sity of chemical action between two substances determines
the electromotive force of the current, it is the quantity of
substances uniting which determines its amount. The unit
of quantity of current (Q) is termed a coulomb ; it is one very
little used, and is the amount which a strength of one ampere
gives in one second. Measured by the method of electrolysis,
it is that which deposits -000162 grain of hydrogen, '0051035
grain of copper, or '017343 grain of silver.
Density of Current. This means merely the strength of
current passing through a given section of a conductor, or into
or out of a given sized surface of electrode. No unit of it
has hitherto been commonly recognised, but I have proposed
( 29)
(Proc. of Birm. Phil Soc., Vol. III., p. 277) the unit strength
of current entering a surface of one square centimetre of
cathode as a convenient one.
Density of current at the surface of the electrodes is one of
the most important circumstances in electrolysis. Variation
of it has often great effect both upon the physical structure
and chemical composition of deposits upon cathodes ; the
former has already been described. It also appears to affect
the properties of oxygen and chlorine when they are sepa-
rated at the anode. Metals which are easily oxidised, such as
cobalt, are deposited upon cathodes in a state of oxide or
basic salt if the density of the current at that surface is small,
but in the state of metal if it is great. It was largely by
increasing the density of the current that Davy succeeded in
isolating potassium. Any circumstance, such as polarisation,
which diminishes the density of the current, is liable to affect
the properties and composition of the deposit.
Quincke has shown that the force tending to separate the
elements of an electrolyte is proportional to the strength of
the current per unit of sectional area of the liquid ; that it
increases with the electromotive force of the current, and is
inversely proportional to the length, but independent of the
cross section and conductivity of the liquid, if the resistance
of the remainder of the circuit is small in comparison with
that of the electrolyte (Journal of the Chemical Society,
Vol. X., p. 208).
Distribution of Current in Electrolytes. With a per-
fectly homogeneous electrolyte of much larger section than
the opposed surfaces of the electrodes, and the latter placed
centrally and symmetrically in it, when the current leaves
the anode it spreads out in the liquid in curves not unlike
those of magnetism diverging from the poles of a magnet,
and the densest portion of the current is in the central axis
joining the electrodes. Its distribution in the liquid has
been investigated by Tribe, who suspended little bits of
metal in different parts of a cross section of the solution,
and ascertained the amount of electrolytic action produced
upon them by the same current, during the same period
(Proceedings Royal Soc., Vol. XXXI., p. 320; Vol. XXXIL,
p. 435).
Relative Amounts of Currents produced by Different
Metals. Equal weights of different metals yield by voltaic
action different amounts of current. Whatever amount of
current a particular weight of any given metal requires in
order to deposit it, that same amount will it yield by voltaic
action ; its generating and consuming powers in relation to
electric current are therefore equal. The amount of current
produced by a given weight of a particular metal depends
(30)
both upon the atomic weight and upon the degree of valency
of the metal. An atomic weight of a monad metal yields one
equivalent quantity of current ; one of a dyad yields two ; a
triad three ; and so on.
The percentage of equivalent of external current actually
obtained is, however, in practice extremely variable, and the
full proportion is rarely obtained. This arises from the cir-
cumstance that a greater or less proportion of the current
generated circulates in minute local circuits upon the surface
of the dissolving metal, and does not enter the external cir-
cuit at all. By actual experiment in nearly one hundred
cases of various kinds, I found that the proportion of external
current varied from about 2 to nearly 100 per cent.
Electrolytic Arrangements. Various combinations and
arrangements have been employed in which chemico-electric
currents produce electrolysis ; and these arrangements have
been classified as follows : 1. Electrolysis by simple contact
of one metal with one liquid ; 2. By contact of one metal with
two liquids ; 3. By contact of two metals with one liquid ; 4.
By contact of two metals with two liquids ; 5. By a separate
electric current ; and 6. By a separate current and a series of
electrolysis vessels.
The first of these arrangements is termed the " simple
immersion process," the most familiar example of which is the
coating of iron with copper by simply dipping it into a solu-
tion of cupric sulphate. In this process the voltaic currents
are excessively minute, are generated in immense numbers at
points inconceivably small all over the immersed surface of the
metal, and re enter producing electrolysis at all the inter-
mediate points of that surface. In this arrangement the
actions and products at the anodes cannot conveniently be
observed or separated from those at the cathodes. The deposit
of metal obtained by it is usually very thin.
The second consists in either carefully placing a lighter
liquid in a distinct stratum upon a heavier one, or separating
the two by means of a porous partition, and immersing the
metal in contact with the two liquids. The portion of metal
in one liquid then generates a current which re-enters the
other part, or the second piece of the same metal in the second
liquid, and produces electrolysis. By this contrivance the
negative portion of the metal receives an electrolytic deposit
in a liquid which the metal itself is unable to decompose by
simple contact.
The third consists in bringing two metals into contact at
their upper ends, either without or by means of a wire, and
immersing their lower ends in the liquid; or allowing the
metals to touch each other in the solution. Under these cir-
cumstances a current passes from the positive metal through
( 31 )
the liquid into the negative one, producing electrolysis, and
returns by the external circuit ; the positive metal also acts
simultaneously by "simple immersion process." This con-
trivance also enables the negative metal to receive an electro-
lytic deposit in a liquid which it does not decompose by
" simple immersion," because the second metal offers a second
path of return for the re-entering current. Cases of self-
depositing metals acting by this process have long been
recorded, in which a metal immersed in a solution of the
same metal has produced a metallic deposit, e.g., with cadmium
in contact with copper in a boiling hot saturated solution
of cadmic chloride the copper becomes coated with that metal.
These cases have been but little investigated. Under this
arrangement may be classed the "two metal" couples of
Gladstone and Tribe, in which the resistance is greatly
diminished, and therefore the strength of the current in-
creased, by making the circuits indefinitely small. This is
effected by electrolytically depositing copper, silver, or
platinum in a porous spongy layer upon the surface of zinc or
magnesium, washing the plate so prepared, and immersing it
in the liquid to be electrolysed.
The fourth is termed the "single cell process," and consists
of two liquids separated by a porous partition, the two metals
being partly immersed, one in each liquid, and in contact with
each other externally, or connected together outside by means
of a wire. This method also enables a deposit to be produced
upon a metal which does not decompose the liquid by simple
contact. In this and the second arrangement, however, the
liquids gradually diffuse into each other, waste the positive
metal by simple immersion process, " and disturb the action at
the negative surface."
The fifth is the most convenient arrangement, and the most
frequently employed. It consists of a vessel containing the
electrolyte and two electrodes, neither of which spontaneously
decomposes the solution, the electrodes being connected with
the battery or other source of current by means of two wires.
It is known as the "battery process," or "separate current
process." By it the strength of current in relation to the
resistance in the electrolysis cell may be indefinitely increased,
the most incorrodible metals may be used as anodes, and with
a sufficiently dense current and suitable liquid even the alkali
metals may be deposited. The sixth arrangement consists
merely of a single series of such vessels and electrodes with an
undivided current passing through the whole of them. It is
not much employed.
Self-Deposition of Metals. Eaoult, also Gladstone and
Tribe, have discovered some new cases of electrolysis of this kind.
Raoult states (Comptes Rendus, Vol. LXXV., p. 1,103) that when
(32)
two plates, one of copper and one of cadmium, are completely
immersed in a solution of cadmic sulphate deprived of air, and
covered with a layer of oil, as long as they do not touch each
other, a very slight evolution of hydrogen is seen on the
cadmium plate, whilst the copper shows no visible change.
When, however, the plates are caused to touch each other,
cadmium at once begins to be deposited on the copper one.
Couples of gold iron, gold nickel, gold antimony, gold lead,
gold copper, or gold silver, immersed either in cold or hot acid
or neutral solution of salts of the more positive of these two
metals, yielded no deposit of that metal (Journal of Chemical
Society, 2nd series, Vol. XL, p. 464). Gladstone and Tribe
also observed that a copper zinc couple separated zinc from a
1-5 per cent, aqueous solution of zinc sulphate (ibid. p. 453).
Other instances of self-deposition will be given.
As these deposits of cadmium and zinc did not appear in
solutions of the nitrates of those metals, and as an oxide of
metal appears to be formed upon the corroded or positive
plate, a probable explanation of the formation of the metallic
deposits is that the water is decomposed, the salts in con-
tact with the negative plate are reduced to the metallic state
by the nascent hydrogen, and the acid thus formed is pre-
vented from corroding the deposited metal by being imme-
diately removed from it by diffusion into the mass of the
liquid. Another arrangement in which a metal deposits
itself is well known. It is that in which one metal is in con-
tact with two different liquids, one of them being a solution
of a salt of that metal.
Methods of Preparing Solutions for Electrolysis. The
exact details of preparing solutions for electro-chemical
action differ of course in every different case. There are,
however, two general methods the one termed the chemical,
and the other the battery or separate current process. In the
former the usual processes of oxidation, crystallisation, solu-
tion, &c., are employed, and may be found sufficiently
described in any work on general chemistry. The latter
usually consists in taking a suitable solvent, hanging in it a
large anode of the particular metal and a proper cathode, and
passing a current until sufficient of the metal is dissolved and
the liquid yields the desired deposit. The liquids obtained
by the two processes, however, are not always exactly the
same in chemical composition, because the electric process is
attended by chemical changes at the cathode. In the latter
process the anode is sometimes immersed in a portion of the
liquid in a porous cell, the latter being partly immersed in the
remainder of the solution.
Eleetro-Chemistry of Individual Substances. Usually,
electro-negative bodies appear at the anode, and electro-
( 33 )
positive ones at the cathode; iodine, however, also sulphur,
and less frequently selenium, appear either at the anode or
cathode, according to the electric character of the body it is
separated from, and in rare cases the same element is liberated
at both electrodes simultaneously e.g. t iodine from an aqueous
solution of iodic acid.
The degrees of facility with which different substances are
separated from their compounds, and the conditions of elec-
trolytic balance of substances at their points of commencing
separation, are subjects which have been but little examined,
and require much investigation. Extensive tables will yet be
formed showing the degrees of electromotive force in volts,
and the density of current required to separate particular
substances from certain liquids under given conditions.
General truths will thus be evolved, throwing light upon the
magnitude of the influence we term " chemical affinity " and
upon the molecular relations of bodies, showing us also why
some substances are easy and others difficult to separate. A
systematic examination of the conditions under which allied
substances, particularly chlorine and oxygen, are set free
would probably enable us to determine those under which
fluorine could be liberated. It is not by misdirected strength
of current, however great, particular bodies are obtained, but
by properly directed energy. From a weak solution of a
potassium salt, even the strongest current with a large solid
cathode will not secure to us the metal, but by using a
cathode of mercury of small surface, even by means of a
current of low electromotive force, potassium has been
isolated. The laws of nature are universal, and electrolysis is
no exception to the truth of the general statement that the
x^hief secret of success in all things is well-directed energy.
As the study of electro-chemistry includes a knowledge not
only of the conditions under which a given substance is elec-
trolytically separated, but also of the electrolytic effect of a
current or individual compounds, both are described in the
following sections, and the series of substances are treated in
systematic order.
Electrolytic Separation of Hydrogen. H. Electro-chemical
equivalent = l.oc^(A monad cation. The only known gaseous
metal. Is very readily separated ; it is set free in a very large
number of cases where water, acids, or other salts of hydrogen
are electrolysed. In some cases it is set free by direct action,
as when zinc or any other metal more electro-positive than
hydrogen is immersed in the above liquids. In other cases it
is liberated by " secondary action," as when those metals more
electro-positive than hydrogen are electro-deposited from
aqueous or acid solutions, and subsequently decompose the
liquid by simple contact.
(U)
It is separated by all the electrolytic processes. Its libera-
tion and subsequent spontaneous ignition when potassium is
placed upon water is one of the most familiar and striking ex-
periments of electro-chemistry. Magnesium, and especially
its amalgam with mercury, decomposes water, setting free
hydrogen. The same metal also liberates hydrogen from a
great variety of saline solutions. Nearly all the readily
oxidable metals decompose acidulated water, and the in-
stances are so numerous that to specify all of them is quite
unnecessary. According to H. St. Claire Deville, silver evolves
hydrogen rapidly from aqueous hydriodic acid; and even
silver, gold, and platinum, when in a finely divided state,
liberate hydrogen from a hot concentrated solution of potassic
cyanide.
I have observed the following cases relating to separation of
the gas by magnesium. That metal did not evolve hydrogen
by simple immersion in dilute hydrofluoric acid, and only a
little in an aqueous solution of potassic chloride, but evolved
it freely in a mixture of the two liquids. Similarly with the
same acid and a solution of chlorate of potassium. It did not
evolve the gas in a mixture of the same acid and a solution of
potassic perchlorate. It set free hydrogen from a mixture of
that acid and a solution of potassic bromide; but not from
either alone. Similarly with magnesium in hydrofluoric acid
mixed with solution of potassic iodide ; but not with that acid
when in admixture with solution of potassic iodate. It set
free hydrogen from a mixture of that acid and solution of
potassic sulphate ; but not from either liquid alone. Probably
the absence of gas was due, in some of these cases, either to-
the formation of a film of magnesic fluoride or suboxide upon
the surface of the metal, and the insolubility of that salt in the
particular liquid.
Some anhydrous hydrogen acids yield hydrogen readily by
electrolysis ; others do not. With platinum electrodes and a
separate current from ten Smee cells, anhydrous hydrofluoric
acid at 0C. was freely decomposed ; but anhydrous hydro-
chloric acid, liquefied by great pressure at 0C., scarcely con-
ducted at all, and evolved no visible gas.
Nearly all aqueous acids yield hydrogen at the cathode by
the separate current process. This accords with G. Wiede-
mann's observation, that mixed liquids are more easily elec-
trolysed than unmixed ones. According to Bourgoin, by
electrolysis with platinum electrodes of distilled water con-
taining pure sulphuric acid, the hydrogen and oxygen
obtained are probably not results of an action of the current
upon the water, nor of liberated electrolytic products acting
upon the water, but of direct decomposition of a hydrate of
sulphuric acid. Concentrated nitric acid does not liberate
hydrogen by electrolysis, the hydrogen being absorbed.
(35)
Aqueous solutions of alkalis frequently yield hydrogen at
the cathode. The electrolytic behaviour of each of the
individual acids, salts, and alkalies, with regard to separation
of hydrogen, &c., will be more fully described under the
heading of the respective substances.
In consequence partly of the very frequent simultaneous
deposition of hydrogen with other metals, those metals often
contain that gas. It has been observed conspicuously in
deposited palladium, and, to a less extent, in iron, cobalt,
nickel, copper, and tin, and it has been stated that the
explosive variety of deposited antimony contains hydrogen ;
but, according to E. Pfeifer, " explosive antimony " contains
no free hydrogen (Jour. Chem. Soc., Vol. XLIL, 1882,
p. 467). Much, however, depends, in all these cases, upon
the kind of solution employed. I have several times observed
that the steel blade of a knife which has been used as a
cathode for a short time, either in a dilute acid, or in an
alkaline liquid, becomes very brittle. Other investigators
have also noticed that the simple immersion of iron in a
dilute acid greatly reduces its tenacity ; and it is not impro-
bable that steam boilers are sometimes weakened by their
decomposing the water and absorbing the hydrogen. It has
been stated by Bottyer that if a piece of palladium, cobalt,
nickel, or tin, has a wire of aluminium twisted round it, and
is then immersed during a few minutes in a dilute acid, it
absorbs sufficient hydrogen to exert a slightly reducing action
upon a solution of potassic ferricyanide, also that a plate of
palladium, previously coated with palladium black, absorbs
the gas more rapidly, and when taken from the liquid and
dried quickly between porous paper becomes red hot in the
air in a few seconds.
For the absorption of hydrogen by platinum in electrolysis,
see Jour. Chem. Soc., 1877, Part II., p. 161, and for the depo-
sition of hydrogen on both electrodes see ibid. Part I., p. 678.
Separation of Oxygen. 0. Electro-chemical equivalent
= 1 = 8. A dyad anion. It is much less frequently or readily
obtained than hydrogen by electrolysis, also less easily than
the least oxidable metals. It is not separated by either of
the electrolytic methods, except those in which a separate cur-
rent is employed. To obtain it requires not only a separate
source of current, but also an anode and liquid not easily
oxidised. It is usually obtained by passing a current by means
of platinum plates through a cooled mixture of one volume of
sulphuric acid, and three to five volumes of pure water. The
gas thus obtained is partly in the state of ozone, which may
be detected by its odour. Numerous other mixtures of water"
with some acid, alkali, or salt, to render the mixture con-
ducting, might be employed for obtaining it, but in all cases
D2
( 36 )
the anode must be a non-corrodible one. The electrolysis of
various substances such as fused oxides, &c., which yield
oxygen, will be described in their appropriate places.
Electrolysis of Water. H 2 0. Molecular weight = 18.
F. Kohlrausch has shown (Dingler's Polytechnik Journal, Vol.
222, p. 283) that perfectly pure water is practically a non-
conductor of the voltaic current (and probably not an elec-
trolyte), and that on the addition of the least trace of im-
purity its conduction-resistance is greatly diminished.
Pure water is rapidly decomposed by simple immersion or
contact of either of the alkali metals, less rapidly by alu-
minium amalgam and by magnesium, and slowly by the
ordinary base metals, in each case by oxidation of the im-
mersed metal. Magnesium amalgam containing one half a per
cent, of magnesium decomposes water with violence, and more
rapidly than sodium amalgam containing twice that per-
centage of sodium (Cailletet, Watts's "Die. of Chem.," Vol.
VI, p. 816). An amalgam of aluminium and mercury
decomposes water at ordinary temperature (A. Cossa, Watts's
"Die. of Chem.," Vol. VII., p. 54). Alloys of aluminium and
gallium decompose water readily, setting free much hydrogen
and nearly the whole of the gallium as liquid metal (Lecoq de
Boisbaudran, Chem. News, Vol. XXXVII., p. 274). Finely
divided iron slowly decomposes boiling water, and sets free
hydrogen (E. Ramann, Jour. Chem. Soc., Vol. XL., 1881, p.
879). Water containing certain acids is decomposed more
rapidly ; boracic acid, cyanide of mercury, sugar, or gum dis-
solved in it have but little effect. The decomposition of water
containing sulphuric acid, by means of zinc, is a common mode
of obtaining hydrogen. Iron filings wetted with water, and
exposed to the air or nitrogen at 60F., induce the formation
of ammonia (Berzelius).
Gladstone and Tribe state that pure water may be decom-
posed by a " copper-zinc couple," also by iron or lead which
has been previously coated electroly tically with spongy copper.
At 0C. the decomposition of water by a zinc-copper couple is
nearly nil; but at 100C. it is very great (Jour. Chem. Soc.,
Vol. XXXV., 1879, p. 572). With a magnesium platinum
couple the decomposition is vigorous, even in cold water
(ibid. p. 576).
According to D. Tommasi, water is not decomposed by a
separate current from a single zinc-carbon or zinc-copper
element if the electrodes are of platinum ; but if the anode is
a metal copper, for instance which, under the influence of
that current, can unite with oxygen, the water is decomposed
(Jour. Chem. Soc., Vol. XLIL, 1882, pp. 134 and 353).
The usual mode of electrolysing water is by previously
mixing sulphuric acid freely with it, and passing a separate
(37)
current through the mixture by means of platinum elec-
trodes ; by this method its' oxygen as well as its hydrogen is
obtained, and a small quantity of the former gas is absorbed
by the water. The oxygen contains a small proportion (but
not more than -^J^ part of its weight) of ozone.
Janeczek considers that in the electrolysis of pure water,
hydrogen at the cathode and hydric peroxide at the anode are
the proximate resultants, and that the peroxide is resolved
into water and oxygen (Jour. Chem. Soc., 1876, Part I., p. 182).
Bouvet electrolysed water under a pressure of several
hundred atmospheres. He found that the amount of water
decomposed by a given quantity of current was independent
of the pressure (Jour. Chem. Soc., Vol. XXXVL, 1879, p. 293).
"Water containing atmospheric air yields ammonia at the
cathode, and nitric acid at the anode (H. Davy).
Separation of Ozone. Ozone is developed by electrolysis
in aqueous solutions of nitric, hydrofluoric, sulphuric, or phos-
phoric acids, also in those of nitre, potassic phosphate, or sodic
sulphate, but not in those of hydrochloric or hydrobromic
acids, or in strong nitric acid, or in aqueous solutions of
metallic chlorides, bromides, iodides, or ferrous sulphate.
According to Houzean (Comptes Eendus, Vol. LXXIV., p. 256),
the electrolysis of water furnishes only 3 to 5 milligrammes of
ozone per litre (Jour. Chem. Soc., Vol. X., 2nd series, p. 220).
Electrolysis of Hydrie Peroxide. H 2 2 . Molecular weight
= 34. Electrolysis gradually resolves peroxide of hydrogen
into hydrogen and oxygen, the proportion of the latter being
greater than in the decomposition of water (Thenard).
E. Schone has electrolysed peroxide of hydrogen, and found
that the results were influenced by the strength of the solu-
tion, the degree of acidification, and the strength of the
current, and concludes that it is not an electrolyte, and that
its decomposition during electrolysis of the water or acid
present is a result of secondary action, due to the liberated
hydrogen and oxygen (Jour. Chem. Soc., Yol. XXX VI., 1879,
p. 878).
According to Berthelot a dilute solution of hydric peroxide
undergoes electrolysis in two different ways viz., one with,
and one without, the evolution of hydrogen, and both of
these may coexist. With high electromotive force both gases
are evolved, but with low electromotive force, such as that of
a zinc cadmium couple, only oxygen is given off", and no
hydrogen gas appears at the cathode. The latter decompo-
sition can be effected by any current, however feeble. In this
case either the peroxide splits up into water and oxygen, or
more probably a secondary action occurs, and the electrolytic
hydrogen combines with undecomposed peroxide to form
water.
(38)
Separation of Nitrogen. N. Electro-chemical equivalent
3/- = 4'66. A triad anion. It is set free (along with other
gases) by simple contact of metallic zinc with ammonic nitrate
in a state of fusion. A concentrated solution of ammonia,
when electrolysed by a separate current and iron electrodes,
yields pure nitrogen at the anode, and hydrogen at the
cathode (Hisinger and Berzelius).
The electrolysis of compounds of nitrogen and hydrogen
will be treated of with the alkali metals.
Electrolysis of Oxides of Nitrogen. The only ones of
these which appear to have been thus treated are hyponitric
(N 2 O 4 ) and ordinary nitric acid (HN0 3 ). The former aqueous
acid conducts slowly, and is decomposed (Faraday). AY.
Zorn prepares hyponitrites by the electrolysis of a solution
of a nitrite by means of a current from four Bunsen cells
ahd mercury electrode?, and stopping the current as soon
as ammonia begins to be evolved. In this reduction hydro-
xylamine is also formed (Jour. Ckem. Soc., Vol. XXXVIIL,
1.880, p. 4).
Nitric acid when concentrated is a good conductor. It
yields with platinum electrodes oxygen, and simultaneously
becomes yellow and then red at the cathode, and finally evolves
gaseous nitric oxide. A more dilute acid yields hydrogen at
the cathode, the quantity being greater as the acid is weaker
and the current more dense ; and if the acid is not of greater
specific gravity than 1-24 and the current not too strong, the
water alone of the acid is decomposed, and the full equivalent
quantity of hydrogen is set free as gas.
By electrolysis concentrated nitric acid is decomposed with
production of nitrous acid; with the acid of sp. gr. 1*2 a feeble
current does not produce this effect. No ammonia is produced
in dilute nitric acid, either per se or in presence of sulphuric
acid ; but if a solution of cupric sulphate is added in sufficient
amount, sulphate of ammonium and metallic copper are simul-
taneously produced until all the nitric acid is converted into
ammonium sulphate. In the presence of free alkali, nitrates
are not converted into ammonia, but the latter is changed
into nitric acid (C. Luckow, Jour. Chem. Soc. t Vol. XXXVIIL,
1880, p. 282).
Brester states (Chem. News, Vol. XVIIL, p. 144) that when
decomposed by electrolysis nitric acid does not evolve any
hydrogen gas at the surface of a cathode of platinum or char-
coal ; the acid is converted into ammonia. Bloxam (Chem.
News, Vol. XIX., p. 289) has shown that the hydrogen set free
from a cathode of platinum in dilute nitric acid, or in a solu-
tion of potassic nitrate, contained in a porous cell, placed in
dilute sulphuric acid containing the anode, converts not more
than one-half of the nitric acid of either of those solutions into
( 39 ;
ammonia. Bourgoin (Comptes Eendus, Vol. LXX., p. 811) has
also electrolysed nitric acid.
The electrolysis of nitric acid, and solutions of its soluble
salts with electrodes of wood charcoal or gas carbon yield
mellogen free from nitrogen (Bartoli and Papasogli, Jour. Chem.
$,YoL XLIV., 1883, p. 592; The Electrician, Vol. X., p. 388,
Vol. XL, pp. 28 and 101).
In the electrolysis of red fuming nitric acid no gas is set
free at first at either electrode. At the anode, N0 4 is totally
changed to N0 5 by oxidation. At the cathode, N0 5 is
reduced to H 3 N during the whole of the electrolysis (A.
Brester, Chem. News, Vol. XVIIL, p. 145).
Finely divided copper, palladium, platinum, or carbon,
charged with hydrogen, convert nitre into potassic nitrite
and ammonia (Gladstone and Tribe, Jour. Chem. Soc. t Vol.
XXXIII., 1878, pp. 306 and 307). Gladstone and Tribe
have also investigated the electrolysis of a solution of
potassic nitrate by a zinc copper couple, and are inclined to
the hypothesis " that the two metals electrolyse the nitrate
of potassium, with formation of nitrate of zinc, the reduc-
tion being effected at the negative pole through the agency
of the potassium" (Jour. Chem. Soc., Vol. XXXIII., 1878,
p. 143). Professor Thorpe also has shown that the copper
zinc couple, in the presence of water and saltpetre, converts
the whole of the nitrogen of the salt, first into nitrite and
then into ammonia (Jour. Chem. Soc. t Vol. XXXIII., 1878,
p. 139).
Passive State of Metals. A peculiar condition, termed
" the passive state," occurs with various metals when used as
electrodes in nitric acid. By the following methods a platinum
wire, to be used as the cathode in nitric acid of 1'49 sp. gr.,
and in which, with a suitable density of current, it would
usually evolve gas for a time only, will be caused to evolve no
gas from the moment of immersion. 1st. By connecting and
then immersing the two polar platinum wires together in the
liquid, and then at once separating them. (In this case, how-
ever, the acid must be diluted with less than its own volume
of water.) 2nd. By igniting the cathode, and then immersing
it after the anode. 3rd. By taking a second platinum wire,
and after the cathode has ceased to evolve gas, joining the
wire to it outside the liquid, then immersing the wire and
withdrawing the cathode. The fresh cathode will then evolve
no gas from the commencement, and this property may be
transferred by it to a third wire, and a fourth one, and so on.
A wire which has lost the power of liberating hydrogen
recovers it by exposure to air, the time required being longer
as the acid is stronger. In all these cases, if the current is
too strong gas will be evolved. (Gmelin's "Handbook of
(40)
Chemistry," Vol. L, pp. 253-362. See also A. Brester, Chart-
News, Vol. XV1IL, p. Hi.)
Separation of Fluorine. F. Electro-chemical equivalent
19. A monad anion. I have made many attempts with this
object by electrolysing anhydrous hydrofluoric acid, with,
anodes of carbon, platinum, palladium, and gold ; also by elec-
trolysing certain fluorides in a state of fusion. In none of
these cases, however, was that element definitely obtained-
These experiments will be briefly described under the head-
ings of the respective substances.
Electrolysis of Anhydrous Hydrofluoric Acid. H.F.
Molecular weight = 20. I have examined this highly dan-
gerous and extremely volatile liquid. It boils at 67T..
Potassium immersed in the chilled acid evolved hydrogen, andr
produced vivid combustion. Sodium acted as it does upon
water. The noble and basa metals did not decompose it.
Magnesium, aluminium, zinc, cadmium, tin, lead, reduced iron,
powdered arsenic, antimony, or bismuth, did not expel hydro-
gen from it.
I electrolysed the chilled fuming liquid by means of a
separate current with a platinum anode ; it conducted much
more readily than pure water. With four Smee elements it
began to conduct visibly, and with ten it conducted readily.
No odour of ozone was evolved. The anode gradually ac-
quired a thick red-brown crust, which deliquesced in the-
atmosphere. With forty elements the conduction was copious,
the anode rapidly corroded, and much finely-divided platinum
collected in the liquid. The brown coating was insoluble in
the acid, but dissolved with formation of a basic salt in water,
and formed a blood-red liquid. With an anode of very close-
grained gas carbon, and six Smee cells, conduction occurred
freely, and the carbon rapidly disintegrated. Anodes com-
posed of fifteen different kinds of carbon of dense woods were
tried with a current from ten elements; those made from
kingwood, beech, ebony, boxwood, and lignum vitse were the-
best. On immersing them in the acid, even without a current,
they evolved bubbles (of air ?), cracked, and flew to piece?,
and on passing a current they broke immediately, some with
violence, projecting the fragments and liquid in all directions
even the densest kinds behaved thus. The most resisting
was that made from beechwood. With much difficulty, and
by the aid of a magnesium light, it was ascertained that the
paFsige of the current was not attended by any increase of
bubbles from the carbon. No special odour besides that of
the acid could be detected, but the charcoal, when removed
from the liquid, emitted a feeble chlorous odour, as well as-
that of the acid.
With forty Smee elements and an anode of gold the acid
scarcely conducted at all ; in half an hour the gold was some-
what corroded, and acquired on its edges a few green crystals,
which became red by contact with the moisture of the atmo-
sphere. With a palladium anode the acid conducted mora
freely, but less so than with one of platinum or charcoal. A
current from forty Smee elements caused a palladium anode-
to corrode, and become covered with a thick brittle crust of a
dark red-brown colour upon its outer surface and a brighter
red beneath. By prolonged action a quantity of this substance
was collected on a plate of platinum upon a heated block of
iron, and was subsequently investigated.
In each of these experiments the acid was contained in a
large platinum cup immersed in a freezing mixture. The cup
was provided with a lid of paraffin to exclude moisture, for
which the acid has most intense attraction ; it was also divided
vertically in the middle by a plate of paraffin, which extended
to within about half an inch of the bottom of the vessel, in
order to prevent evolved hydrogen touching the anode deposit-
and rapidly reducing it to metal.
Electrolysis of Aqueous Hydrofluoric Acid. According to
Faraday, aqueous hydrofluoric acid is not decomposed by-
electrolysis, but only the water in it. I electrolysed the pure-
dilute liquid containing about 10 per cent, of the acid, by
means of a separate current and sheet platinum electrodes.
Gas was evolved freely from each electrode, and a very strong,
odour of ozone was observed. No corrosion of either electrode
occurred during twelve hours' action. The gas from the anode
was collected ; it re-inflamed a red hot splint vividly ; paper
wetted with spirits of turpentine was not blackened, nor was
bright silver tarnished by it; it was oxygen. I similarly
electrolysed, by a current from ten Smee cells, the pure
aqueous acid containing about 80 per cent, of the anhydrous
substance. Copious conduction took place, with much evolu-
tion of oxygen at the anode. Heat was produced in the liquid ' r
the anode dissolved slowly; in three hours it lost 1*58 grain.
The smell of ozone disappeared if the electric current was
much weakened, and reappeared on first contact. In a
further eleven hours, the anode lost 5 '05 grains, and was
covered with a blackish crust which was partly soluble in
water to a brownish solution. In a further twenty hours the
loss had increased from 5 '05 to 15 '00 grains, without any signs-
of metallic deposit upon the cathode.
I also electrolysed during five hours a chilled mixture of
160 grains of the anhydrous acid, 244*4 grains of concen-
trated nitric acid, and 273*8 grains of pure water, by means
of sheet platinum electrodes and six Smee elements. Free-
conduction occurred, and much odourless oxygen was evolved,.
(42)
The anode was not corroded, and no gas was visible at the
cathode. By similar electrolysis with a current from ten
Smee cells of a mixture of equal volumes of 30 per cent, pure
aqueous hydrofluoric acid and strong hydrochloric acid,
much chlorine was set free from the anode and hydrogen
from the cathode. This is consistent with the usual effect
that chlorides, like oxides, are decomposed before fluorides.
A mixture of equal volumes of the aqueous acid and strong
oil of vitriol yielded much oxygen and a strong odour of
ozone at the anode and hydrogen freely at the cathode.
The anode corroded very slowly, and fumes were evolved
which rapidly blackened gutta percha. With selenious acid
in place of the sulphuric, gas was set free at both electrodes,
and much red selenium was deposited upon the cathode.
No odour of ozone was evolved until a large quantity of red
and black selenium had been deposited ; it was then evolved
freely. The anode was not corroded during twenty-eight
hours' free electrolysis. By electrolysis of the dilute hydro-
fluoric acid, to which some phosphoric anhydride had been
added, ozone was evolved from the anode and hydrogen from
the cathode ; the anode was also slowly corroded.
Bartoli and Papasogli have also electrolysed aqueous hydro-
fluoric acid with anodes of wood charcoal or gas carbon, and
found the anodes disintegrate (The Electrician, Vol. XL, pp. 28
and 101 ; Jour. Chem. Soc., Vol. XLIV., 1883, p. 590).
Separation of Chlorine. 01. Electro-chemical equivalent
= 35*5. A.monad anion. Set free on passing, by means of an
anode of carbon or platinum, an electric current through con-
centrated hydrochloric acid, or through aqueous solutions of
the chlorides of sodium, ammonium, or other metals, also
through various chlorides in a state of fusion. With aqueous
solutions, some of the chlorine usually dissolves in the liquid.
The electrolysis of chlorine water yields hydrochloric acid at
the cathcde and a little chloric acid at the anode (Balard,
also Connell, Gmelin's "Handbook of Chemistry," Vol. I.,
p. 451).
Electrolysis of Hydrochloric Acid. HC1. Molecular weight
= 36*5. I ascertained by experiment (Proc. Roy. Soc., May 4,
1865) that the anhydrous substance, liquefied by great pres-
sure, is a very feeble conductor of electricity. Two fine
platinum wires immersed in it jths of an inch in length and
-j^th of an inch asunder, and connected with ten Smee elements,
evolved no perceptible bubbles of gas, and produced only a
small deflection amounting to 23 of the needles of a sensitive
galvanometer; and this amount of conductivity might possibly
have been due to a minute trace of oil of vitriol mixed with
the liquid acid. In a second similar experiment, with the
wires -j^th of an inch apart, not the slightest conduction
(43 )
occurred on using the same battery power, but by employing
the secondary current of a strong induction coil, with con-
denser attached, conduction and a steady deflection of 20 of
the needles took place, gas being freely evolved from the
negative wire only. It is evident, therefore, that liquefied
hydrochloric acid is a very bad conductor of electricity.
Bleekrode subsequently discovered (Proc. Roy. Soc., Vol. XXV.,
1876, p. 325) that the anhydrous liquefied acid "opposes a
formidable resistance, and is not decomposed in a perceptible
way" by the passage through it of a current from 5,G40 cells
of De la Rue's chloride of silver battery.
Gallium liberates hydrogen freely by simple immersion in
dilute hydrochloric acid (M. Lecocq de Boisbaudran).
Electrolysis of concentrated hydrochloric acid with a plati-
num anode causes the anode to dissolve, but that of the dilute
acid causes the formation of chlorine compounds at the anode
without corroding the platinum (D. Tommasi, Jour. Chem. Soc.,
Vol. XLIV., 1883, p. 142).
In dilute solutions of metallic chlorides by electrolysis
hypochlorous acid is alone produced; in concentrated ones
chlorine is also set free. Chlorates are produced from the
chlorides of the alkalies and alkaline earths, as soon as the
reaction of the solutions has become alkaline, from the evolu-
tion of the chlorine and hypochlorous acid (C. Luckow, Jour.
Chem. Soc., Vol. XXXVIII., 1880, p. 282). If dilute chloride
solutions contain a little free hydrochloric acid, hypochlorous
acid is alone produced, and the solution, after a time, acquires
an alkaline reaction.
The electrolysis of aqueous solutions of certain metallic
chlorides by means of the contact of two metals has been
investigated by Gladstone and Tribe (Phil. Mag. [4], Vol.
XLIX., p. 425), and will be described under the headings of
the respective metals. Thorpe has shown that the copper
zinc couple reduces chlorate of potassium to chloride (Glad-
stone and Tribe, Jour. Chem. Soc., Vol. XXXIII., 1878, p. 147).
Platinum charged with hydrogen behaves similarly (ibid.,
p. 309), but more powerfully.
Electrolysis of Oxides of Chlorine. Very little has been
done in this part of the subject. Aqueous solution of oxide
of chlorine (C10 2 ) yields hydrogen at the cathode and a small
quantity of oxygen gas and perchloric acid at the anode
(Count Stadion). I have electrolysed aqueous chloric and
perchloric acids with anodes of silver.
Separation of Bromine. Br. Electro-chemical equivalent
= 80. A monad anion. It is separated in many cases when
aqueous solutions of bromides are electrolysed by means of
a separate current and an incorrodible anode. A portion of
the liberated bromine usually dissolves in the liquid, an
(44)
aqueous solution of bromine yields by electrolysis hydrobromic
acid, and a mere trace of hydrogen at the cathode, but no-
bromic acid at the anode. The water is decomposed (Balard,
also Connell, Gmelin's "Handbook of Chemistry," Vol. I,
p. 451).
Electrolysis of Hydrobromic Acid. HBr. Molecular weight
= 81. Bleekrode has stated (Proc. Roy. Soc., Vol. XXV.,
p. 323) that anhydrous hydrobromic acid is a non-conductor to
the voltaic current from eighty Bunsen eLments. The
aqueous acid when electrolysed by a separate current liberates
bromine at the anode and hydrogen at the cathode.
Electrolysis of Oxides of Bromine. I have been unable
to find any record of any one having electrolysed either bromic
or perbromic acids, or aqueous solutions of their salts.
By immersing a sheet of aluminium in an aqueous solution of
bromic acid, I observed that hydrogen and bromine were set
free.
Separation of Iodine. I. Electro-chemical equivalent =
127. A monad anion. It is, however, sometimes separated
by secondary action at the cathode. According to Bleekrode
(ibid.) liquid anhydrous hydriodic scid does not transmit any
current from eighty Bunsen elements. Faraday observed that
by electrolysis, with a separate current, of potassic iodide, or
iodide of lead, in a state of fusion, iodine was set free at the
anode. A solution of iodine in water yields by electrolysis
some hydrogen at the cathode. The water is decomposed
(Balard, also Connell, Gmelin's "Handbook of Chemistry,"
Vol. L, p. 451).
Electrolysis of Aqueous Hydriodie Acid. A concentrated
solution of aqueous hydriodic acid yields by a separate current,
and platinum electrodes, iodine alone at the anode ; but &
dilute one yields iodine and oxygen (Faraday). Matteucci
observed that the stronger the current, and the more dilute
the acid, the greater was the proportion of oxygen.
If the solution of an iodide be covered with starch jelly, the
cathode be placed in the former, and the anode in the latter,
the starch is turned blue around the anode, even if the solu-
tion contain a much larger quantity of bromide or chloride
than of iodide (Steinberg, Jour. Pr. Chem., Vol. XXV., p. 288;
Watts's " Dictionary of Chemistry," Vol. III., p. 287).
Eiche states (Comptes Piendus, VoL XLVL, p. 348) that iodic
acid (HI0 3 ) is produced by electrolysis of aqueous iodine, or
an aqueous solution of hydriodic acid. In the latter case the
acid is simply oxidised to iodic acid by oxygen evolved by the
decomposition of water. In the former case the iodine is
first ccn/erted into hydriodic acid, and then oxidised in this
way.
(43)
Electrolysis of Oxides of Iodine, &e. By immersing a
sheet of aluminium in a solution composed of twenty-six
grains of dry iodic acid and five ounces of water, I observed
that much gas was evolved ; the metal acquired a strong
odour of absorbed iodine, and had increased about 16 per
ent. in weight (Proc. Birm. Phil Soc., Vol. IV., Part I.)
A solution of one part of iodic acid and ten parts of water
yields oxygen gas at the anode and iodine alone at the
-cathode, the latter being separated by secondary action of
hydrogen, liberated by the electrolysis of the water (Connell).
According to Buff, however (Ann. Chem. et Pharm., Vol. CX.,
p. 257), the iodic acid is resolved by the current into hydro-
gen and iodic anhydride, which latter is decomposed by the
water, thus producing iodic acid and free oxygen (Watts's
"Dictionary of Chemistry," Vol. III., p. 300). The electrolysis
of periodic acid does not appear to have been yet examined.
When an iron or copper plate, or better, a zinc and copper
plate, connected externally by a wire, are immersed in strong
solution of potassium iodate at 60 R, complete reduction to
potassic iodide occurs. Potassium bromate is similarly reduced
to bromide; but potassic chlorate slowly and incompletely
to chloride (G. Peliagri, Watts's "Dictionary of Chemistry,"
Vol. VIIL, Part 2, p. 1,668).
Electrolysis of Bromide of Iodine. When an aqueous
solution of starch and iodine, which has been turned yellow by
dissolved bromine, is subjected to electrolysis, it becomes
orange coloured at the anode by liberation of bromine, and
blue at the cathode by separation of iodine (De la Rive, Ann.
Chem. et Phys., Vol. XXXV., p. 164).
Electrolysis of Iodides, Bromides, and Chlorides. By
electrolysis, iodine and bromine are separated from solutions
of iodides and bromides. lodates and bromates are produced
simultaneously from the iodides and bromides of the metals
of the two first groups, especially in concentrated solutions.
When the solutions of the chlorides, bromides, and iodides
contain free alkali, only chlorates, bromates, and iodates are
produced. From the insoluble compounds of chlorine, bromine,
and iodine, with the metals, suspended in dilute sulphuric or
nitric acid, the acid radicle appears at the anode and the
metal at the cathode (C. Luckow, Jour. Chem. Soc., Vol.
XXXVIII., 1880, p. 282).
Separation of Carbon. C. Atomic weight = 12. A tetrad
cation. " An excess of silicon fused with potassic carbonate
sets free carbon." Deville states that metallic aluminium
liberates carbon from carbonate of potassium in a state of
fusion (Chemist, New Series, Vol. IV., p. 481). I have observed
the same with fused sodic carbonate. According to Phipson,
(46)
magnesium by contact with fused carbonate of sodium set free
carbon abundantly (Proc. Roy. Soc., 1864, Vol. XIIL, p. 217,
also Chemical News, Vol. IX., p. 219).
The following are some experiments of mine (Proc. Birm.
Phil. Soc., Vol.. IV.) : A fused mixture of 200 grains of pure
sodic hydrate, 170 grains of pure precipitated silica, and
610 grains of the mixed anhydrous carbonates of sodium
and potassium was electrolysed by means of a current
from ten Smee elements, with a sheet platinum anode and
a thick platinum wire cathode. Conduction was free, and
much oxygen, which relighted a red-hot splint, was liberated
at the anode. Dark streams flowed from the cathode, sodium
was also set free, and if the cathode was only slightly
immersed bubbles of vapour of sodium were emitted, and took
fire at the surface of the liquid. After one hour's action the
platinum anode had lost '37 grain in weight. The cathode
had a feebly adherent rough deposit of a dull jet black colour
upon it. This deposit was subsequently washed and dried ; a
portion of it burned with a glow when heated to redness, and
left a minute residue of grey platinum; it also deflagrated with
fused nitre below a red heat, and vividly by heating with
potassic chlorate. It did not dissolve nor evolve any gas in a
mixture of strong nitric acid and pure concentrated hydro-
fluoric acid. It was, therefore, carbon.
As carbon was not readily deposited from the fused car-
bonates of potassium and sodium, whilst silicon was deposited
from fused silicon* uoride of potassium, and as "an excess of
silicon fused with potassic carbonate sets free carbon, but
silicon with an excess of the carbonate liberates carbonic
oxide," the carbon liberated in this experiment may have
been a secondary result, and an effect of previously deposited
silicon reacting upon the fused mixture. It was with the
expectation of this effect that I employed silica in the mixture.
I also electrolysed in a platinum cup a fused mixture of
47 5 '2 grains of 97*1 per cent, sodic carbonate (containing as
impurity only water) and 217'4 grains of borofluoride of
sodium, by means of the same current, a sheet platinum anode
and thick platinum wire cathode. Conduction was free. Gas
arose from the anode, and a small amount of black deposit
formed upon the cathode. After having been well washed
the deposit was dried, put on a platinum dish, and heated to
redness; it burned with sudden incandescence until nearly
the whole was consumed. It was, therefore, nearly wholly
carbon.
I electrolysed in a platinum cup a fused mixture of 274
grains of pure sodic carbonate, 375 grains of pure potassic
carbonate, both anhydrous, and 206 grains from crystallised
boracic acid, at a red heat, by means of a current from eight
Smee elements and platinum electrodes. There was free con-
(47)
duction, much gas from the anode, and an instant jet black
deposit formed upon the cathode, and could be burned off
at a red heat. Metallic sodium was set free at the cathode,
especially during deep immersion. The anode was soon much
corroded, and acquired a very smooth surface, and platinum
was deposited upon the cathode. No free carbon was ulti-
mately found.
Electrolysis of Carbonic Anhydride. C0 2 . Molecular
weight = 44. I have examined (Phil. Trans. Roy. Soc., 1861)
the action of a voltaic current on carbonic anhydride liquefied
by great pressure. With electrodes of thin platinum wire
y^th of an inch apart, and the liquid below 32F., not the
slightest conduction occurred with a current from forty Smee
elements ; and sparks from a Euhmkorff coil, which passed
through f-ths of an inch of cold air in an alternate portion of
the divided circuit, would not pass through the liquid. In
another trial, with the wires about T yh of an inch asunder,
sparks from the coil, which were passing freely through
s 9 2-nds of an inch of cold air in the alternate circuit, passed
occasionally through the cold acid and exhibited a pale blue
colour. The liquid is, therefore, a strong insulator of elec-
tricity. Bleekrode also (Proc. Eoij. Soc., 1876, p. 325) tried
the same liquid with a current from 5,540 chloride of silver
elements. A spark jumped between the poles, and the tube
exploded. He concluded that the liquid is a very bad con-
ductor. Cailletet (Comptes Bendus, Vol. LXXV., p. 1,271) has
also arrived by experiments at the same conclusion.
I tested by experiment in an approximate manner the
relative degrees of conduction resistance of distilled water,
and of the same saturated with carbonic anhydride at 60F.
and at atmospheric pressure. No conspicuous difference was
observable.
I also passed an electric current from four Smee elements
by means of platinum wires during one week through very
dilute sulphuric acid in a large \J glass tube, one leg of which
was kept full of a mixture of carbonic oxide and carbonic
anhydride gases. No carbon was deposited. Fuming
sulphuric acid, also a syrupy solution of phosphoric acid,
were saturated with dry carbonic anhydride, and then electro-
lysed by means of platinum wire electrodes and currents from
112 Smee cells in single series; no carbon was deposited
(Proc. Birm. Phil Soc., Vol. IV.).
Electrolysis with Anodes of Carbon. According to A.
Bartoli and G. Papasogli, in liquids whose electrolysis is not
accompanied by evolution of oxygen at the anode, anodes of
wood charcoal, gas carbon, and graphite are not disintegrated
or dissolved, or suffer any loss of weight. In those in which
oxygen is evolved, those anodes are partly disintegrated, and
partly oxidised to carbonic oxide and carbonic acid gases,
together with other products ; graphite used in those liquids
never imparts a colour to the electrolyte, but anodes of wood
charcoal and gas carbon, previously purified, colour it black,
both in alkaline solutions and in those of certain acids and
salts, by the formation of a black substance which they term
mellogen, the composition of which is represented by the
formula C n H 2 4 , together with traces of benzo-carboxylic
acid ; graphite anodes in those liquids produce graphitic acid
C 14 H 2 O 3 . In alkaline electrolytes, anodes of wood charcoal,
.gas carbon, and graphite produce mellic acid C 12 H G 12 ; pyro-
mellic acid C 10 H 6 8 ; hydromellic acid C 12 H 12 ]2 , and another
body, apparently hydro-pyromellic acid, C 10 H 10 8 (Jour. Chem.
Foe., Vol. XLIV., 1883, p. 592; The Electrician, Vol. XL, pp.
28 and 101). For the electrolysis with electrodes of wood
charcoal, gas carbon, and graphite, of solutions of hydrochloric,
hydrobromic, and hydriodic acids and their potassium salts,
potassic cyanide, sulphuric and nitric acids and their salts,
tydrogen and sodium sulphite, arsenic acid, boracic acid,
alkaline hypochlorites, permanganates, bichromates, and
chlorates, chromic acid, mellic acid, oxalates, formiates,
Acetates, &c., and sodic pyrogallate, see also the same paper.
10*9
Separation of Boron. B. Atomic weight = 31, equiv. -^-
= 3-63. A triad cation. By contact of magnesium with boracic
.acid in a fused state boron is set free (Phipson, Proc. Roy. Soc.,
Vol. XIII., 1864, p. 217; also CJiem. News, Vol. IX., p. 219).
" Boron was first electro-chemically isolated by SirH. Davy.
He states that when boracic acid is exposed between two sur-
faces of platinum, receiving at the same time all the action of
n current from 300 cells, an olive brown matter is formed
upon the negative surface, gradually increasing in thickness,
and finally becoming black. The isolated body is boron"
(Chem. Neios, Vol. XII., p. 3).
Electrolysis of Oxide and Fluoride of Boron. Burckhard
states (Chem. Neivs, Vol. XXL, p. 238) that pure boracic acid
in a state of fusion is a non-conductor. I found that by
electrolysing pure borofluoride of potassium in a fused state,
with platinum electrodes and a separate current, boron was
deposited, and combined with the cathode, rendering the latter
rough and brittle.
Separation of Silicon. Si. Atomic weight = 28. A tetrad
cation. According to Golding Bird (Phil. Trans. Roy. Soc. t
1837, p. 37) silicon may be electro-deposited from a solution
of its fluoride in alcohol. The kind of apparatus he employed
was a combination of one voltaic cell in undivided circuit,
with a "single cell apparatus," the silicon being deposited
upon the negative platinum plate of the latter. I electrolysed
in a platinum cup a fused mixture of 300 grains of 97'1 per
cent, pure potassic carbonate (the 2 '9 per cent, being water)
and 442 grains of silico fluoride of potassium, by a current
from ten Smee cells, a sheet platinum anode, and a platinum
wire cathode. Gas arose from the cathode at first only ; after
that streams of black matter poured down from the cathode,
and the latter acquired a blackish film, but subsequently
alloyed with silicon, and fused on its surface.
Separation of Hydride of Silicon. This compound is
obtained, in admixture with much free hydrogen, when the
current from 8 to 12 Bunsen elements is passed by means of
an anode of aluminium containing silicon into an aqueous
solution of common salt. The aluminium dissolves as chloride,
setting free much gas, some of the bubbles of which inflame
spontaneously in the air, emitting a white light, and diffusing
finely divided silica. The compound appears to be due to a
secondary action ; a part of the nascent hydrogen, set free by
union of aluminium with the oxygen of the water, unites with
the silicon (Wohler and Buff, Ann. Chem. et Pharm., Yols.
OIL, CIIL, CIV., and CXIL). It is not stated whether this
compound would be formed by simple immersion without a
separate current. I have observed that a lump of fused silicon,
immersed in a mixture of pure hydrofluoric acid (strong) and
nitric acid, evolves a spontaneously inflammable gas.
By electrolysis, silicic and boric anhydrides are separated
from their concentrated solutions at the anode (C. Luckow,
Jour. Chem. Soc., Vol. XXXVIII., 1880, p. 283).
Becquerel has investigated the decomposition of silicates and
other minerals by electro-capillary diffusion (Comptes Rendus,
Vol. LXVIL, p. 1,081).
Separation of Titanium. Ti. Atomic weight = 50. A
cation. This element does not appear to have yet been
electro-deposited, nor its compounds electrolysed. I observed
that crystals of nitro-cyanide of titanium conducted freely a
current from 60 Smee elements.
For the electrolytic analysis of zirconium, see A. Claessen,
Jour. Chem. Soc., Vol. XLIL, 1882, p. 896.
Separation of Sulphur. S. Atomic weight = 3 2. A dyad
anion ; sometimes also separated by secondary action at the
cathode. Obtained by electrolysing, by means of a separate
current and platinum electrodes, an aqueous solution of sul-
phide of potassium, hydrogen being simultaneously set free at
the cathode (Faraday).
MM. Bias and Miest have shown that if in electrolysis we
replace the anodes of metal by metallic sulphide ores com-
pressed to hard plates, and use a suitable electrolyte, all the
sulphur of the ore is separated at the anode and falls down,
( 50 )
and the metal is deposited upon the cathode (Chem. Neivs, Vol.
(XLVL, pp. 93 and 121 ; The Electrician, Vol. X., p. 388).
Hydric Sulphide. H 2 S. Molecular weight = 34. This
substance when liquefied by great pressure does not appear
to have been yet subjected to the action of an electric current.
Its aqueous solution would no doubt yield sulphur at a platinum
anode. When dilute sulphuric acid is electrolysed with a
zinc anode and a charcoal cathode, hydric sulphide is evolved
at the latter (Highton, Chem. News, Vol. XXVL, p. 117).
Electrolysis of Sulphur Dioxide. S0 2 . Molecular weight
= 64. This oxide, liquefied by pressure, does not transmit a
current from 40 cells. An aqueous solution of the gas yields
sulphur and hydrogen at the cathode by the passage of such
a current (De la Kive, Gmelin's " Handbook of Chemistry,"
Vol. II., p. 170). ^
The electrolysis of its aqueous solution, H 2 SO a , is not
simply a separation of the oxide into oxygen at the anode
and sulphur at the cathode. According to A. Guerout
(Comptes llendus, Vol. LXXXV., p. 225), with a feeble cur-
rent H 2 S0 4 is produced at the anode and a yellow liquid
at the cathode ; with a stronger one sulphur also appears with
the yellow liquid, and with a still stronger sulphur alone is
deposited at the cathode. Its electrolysis resembles that of a
salt, the acid and oxygen being set free at the anode, and the
hydrogen (H 2 ) appearing at the cathode, where it acts upon
a fresh portion of the acid, and reduces it thus : H 2 +
H 2 S0 3 = H 2 S0 2 + H 2 0. This agrees with the fact that hypo-
sulphurous' acid (H 2 2 S) and sulphur appear at the cathode,
the sulphur being produced by the decomposition of that acid
formed there in a concentrated state (Chem. News, Vol.
XXXVI., p. 90).
Sulphurous acid in aqueous solution is decomposed by the
current into sulphur and sulphide of hydrogen, and sulphites
are gradually converted into sulphates. Thiosulphates are
converted into their corresponding sulphates with separation
of sulphur. The alkaline sulphides, according to their rich-
ness in sulphur, are decomposed with or without separation of
sulphur, sulphates being formed. In the alkaline sulphates
and thiosulphates, in addition to sulphides, polythionates are
always produced (C. Luckow, Jour. Chem. Soc.,Vo\. XXXVIIL,
1880, p. 283).
A copper zinc couple liberates sulphur from sulphurous acid
without producing sulphuretted hydrogen (Gladstone and
Tribe, Jour. Chem. Soc., Vol. XXXIII., 1878, p. 307).
Electrolysis of Sulphuric Acid. H 3 S0 4 . Molecular
weight = 98. Sulphuric anhydride (SO.,) is a non-conductor
with a current from 14 Bunsen cells. Its solution in conceu-
(81 )
tratod oil of vitriol is decomposed by a separate current with
platinum electrodes into oxygen at the anode and sulphur at
the cathode. By varying the proportion of the two substances,
part of the sulphur reduces the sulphuric acid to sulphurous
anhydride, which is evolved at the cathode (Geuther, Ann.
Chem. et Pharm., Vol. CIX., p. 130).
By electrolysis, concentrated English sulphuric acid is de-
composed with deposition of sulphur (C. Luckow, Jour.
Chem. Soc., Vol. XXXVIIL, 1880, p. 283).
Separation of Persulphurie Acid. S. 2 r . Berthelot divided
two portions of diluted and chilled sulphuric acid by a porous
partition, immersed stout platinum wire electrodes in the two
portions, and passed a dense current from three very Iarg3
Bunsen cells through the liquids, and thus obtained a mixture
of dilute sulphuric acid containing 88 to 123 grammes of S 7
per litre (Comptes Rendus, No. VII., February 16th, 1880 ;
Jour. Chem. Soc., Vol. XXXVIIL, 1880, p. 607).
Liquid chloride of sulphur, and also carbonic bisulphide, are
non-conductors.
Separation of Selenium. Se. Atomic weight = 79 -5. A
cation ; acts also as an anion. Very little investigation has
yet been made of the electrolysis of compounds of this element.
A mixture of aqueous hydrofluoric and selenic acids yielded
much red selenium upon the cathode. During the electro-
lysis by a separate current of an aqueous solution of selenate
of nickel, containing selenate of sodium and free selenic acid,
I repeatedly observed an abundant deposit of bright red
selenium upon a platinum cathode. The deposition was no
doubt due to decomposition of the free acid, because it ceased
on neutralising the acid with ammonia. According to L.
Schicht (Chemisches Centmlblatt, No. XXIV., 1880; also Berg
und HuUenmannische Zeitung, 1880), selenium is readily and
completely reduced and thrown down by a feeble current from
not more than two cells, both from acid and alkaline solutions
(Chem. News, Vol. XLL, p. 280, Vol. XLIL, p. 331, and
English Mechanic, Vol. XXXL, p. 540).
Separation of Tellurium. Te. Atomic weight = 129. A
triad cation. Ritter, and subsequently Sir H. Davy, observed
whilst electrolysing water with a tellurium cathode that the
water around the cathode acquired a purple colour by dis-
solving telluride of hydrogen, and then precipitated a brown
powder. Magnus showed that the brown powder was metallic
tellurium set free by oxygen, which diffused from the anode,
and decomposed the telluride. If the water is acid the tellu-
ride does not dissolve, but escapes as gas.
L. Schicht states (ibid.) that tellurium is readily and com-
pletely thrown down both from acid and alkaline solutions,
but more readily than selenium. From an acid solution it is
E 2
(02)
easily deposited with a blue-black colour, and from alkaline
ones it is separated in a very loose state at the anode witb
much evolution of gas, and if much metal is present it floats
as a light powder upon the liquid.
Electrolysis of Telluric Fluoride and Chloride. I have
electrolysed pure dilute hydrofluoric acid with an anode of
pure tellurium and a current from a single Smee element. The
action was very slow, and most excellent deposits of bright
reguline metal of grey colour and bright crystalline structure
were obtained. By electrolysing a pure solution of telluric
chloride by means of a very feeble current and large electrodes
of smooth platinum I obtained only a jet black deposit, chiefly
of non-adherent metal.
For the electrolytic purification of tellurium, see Watts's
"Dictionary of Chemistry," Vol. VIIL, Part 2, p. 1,895.
Separation of Phosphorus. P. Atomic weight = 31. A
triad element. Acts both as an anion and a cation. Accord-
ing to Burckhard (Chem. News, Vol. XXL, p. 238), fused
pyrophosphate of sodium yields by electrolysis with a separate
current phosphorus and oxygen at the anode and soda at the
cathode ; if the anode is composed of platinum a phosphide of
that metal is formed.
Electrolysis of Oxides of Phosphorus. The electrolysis of
concentrated phosphoric acid produces a metallic phosphide
with the cathode when the latter is composed of copper or
platinum (H. Davy).
By electrolysis with platinum electrodes dilute solutions
of phosphoric acid or phosphates undergo no change (CL
Luckow, Jour. Chem. Soc., Vol. XXXVIII., 1880, p. 283).
The electrolysis of phosphoric acid and solutions of its salts,
with electrodes of wood charcoal or retort carbon, produces
phospho-mellogen, and with graphite electrodes phospho-
graphitic acid (Bartoli and Papasogli, Jour. Chem. Soc., Vol.
XL1V., 1883, p. 592 ; The Electrician, Vol. XL, pp. 28 and 101).
Chlorides, Bromides, and Iodides of Phosphorus. These
are non-conductors of a voltaic current.
Separation of Arsenic. As. Atomic weight = 75. A triad
cation. Easily separated by various electrolytic processes.
Palladium charged with hydrogen reduces a solution of
arsenious acid to metal without producing arsenide of hydro-
gen (Gladstone and Tribe, Jour. Chem. Soc., Vol. XXXIIL,
1878, p. 308). It is also separated 1. By dissolving arsenious
acid in warm dilute hydrochloric acid and stirring the solution
with a piece of clean copper the latter acquires a coating
of arsenic ; this is the well known " Eeinsch's test " for the-
element ; 2. By contact of zinc with platinum in solutions of
arsenic the latter is deposited upon the platinum ; and 3. By
passing a separate current through a solution of arsenic in,
(53 )
dilute hydrofluoric acid, by means of an anode of arsenic and
a cathode of platinum, I have obtained a scaly deposit of the
metal.
The electrolysis of arsenic acid and solutions of its soluble
salts and electrodes of wood charcoal, or gas carbon, yields
mellogen free from arsenic (Bartoli and Papasogli, Jour.
>Chem. Soc. t Vol. XLIV., 1883, p. 592 ; The Electrician, Vol. XL,
>pp. 28 and 101).
Separation of Arsenide of Hydrogen. AsH 3 . Molecular
weight = 78. From acid solutions of arsenic, magnesium by
simple immersion evolves this poisonous and inflammable
compound (Roussin, Chem. News. Vol. XIV., p. 27). Marsh's
test for arsenic consists in evolving this gas from an acid
solution of arsenic by simple immersion of zinc in it. The
same gas is evolved at a platinum cathode by the passage of a
separate current through solutions of arsenic, when the current
is sufficiently strong. A solid hydride of arsenic, supposed to
have the composition As.H 2 , is produced when water is
electrolysed by a strong current, with metallic arsenic for the
cathode Watts's "Dictionary of Chemistry," Vol. III., p. 181).
Terchloride of Arsenic. AsCl 3 . Molecular weight = 181-5.
This liquid is a non-conductor of a voltaic current, but the
aqueous solution conducts readily and is decomposed.
For the electrolytic analysis of arsenic, see Jour. Chem. Soc.,
Vol. XLIL, 1882, p. 1,320; also Chem. News, Vol. XLVL,
p. 106. And for the detection of arsenic in mineral waters by
means of a voltaic couple of tin and gold, S2e J. Lefort, Jour.
Chem. Soc., Vol. XXXVIIL, 1880, p. 510.
1 on
Separation of Antimony. Sb. Elec. chem. eqt. -~ = 40-00.
3
A triad cation. This metal may be obtained from its solu-
tions by all the methods of electrolysis. It is easily deposited
from an acid solution of its terchloride by simple contact
of various metals. Zinc, bismuth, tin, lead, brass, and
German silver were coated with antimony by simple im-
mersion in that solution; but platinum, gold, silver, nickel,
and antimony were not. The simple immersion process is
used to impart a lilac colour to articles of brass. A small
quantity of hydrochloric acid, which has been perfectly satu-
rated with freshly precipitated and wet teroxide of antimony,
is precipitated by addition of a large bulk of water ; the
mixture is boiled until the precipitate is nearly re-dissolved,
more water is added, and the mixture boiled again in like
manner, and then filtered. The clear liquid is heated to the
boiling point, and then perfectly clean articles of brass are
immersed in it. They at once acquire a film of antimony and
& lilac colour, and, by allowing them to remain a greater or
less length of time, different tints of colour are obtained.
(54)
I have observed that zinc readily deposits antimony as a
black powder by simple immersion in an aqueous solution of
the mixed fluorides of antimony and potassium ; that copper
also deposits it as a black film and powder by contact with the
acid hydrochlorate of terchloride of antimony, and that
crystals of silicon did not become coated with antimony in an
aqueous solution of terfluoride of antimony containing free
hydrofluoric acid ; also, that the oxide of iron upon a rusty
iron wire was rapidly dissolved in a mixture of equal measures
of solution of terchloride of antimony, and a saturated solu--
tion of sal-ammoniac. Watt coats copper with antimony by
immersing it during about half an hour in a solution of one
ounce of chloride of antimony, one pint of spirit of wine, with
sufficient hydrochloric acid added to make the mixture clear.
I have noticed that antimony is deposited by simple immer-
sion from its ordinary chloride, as prepared for pharmaceu-
tical purposes by zinc, bismuth, tin, lead, brass, and German
silver, but not by antimony, nickel, silver, gold, or platinum.
According to Ixaoult, magnesium sets free antimoniuretted.
hydrogen, but no metallic antimony from solutions of the
metal (Chcm. Xews, Vol. XIV., p. 27.) Gold, in contact witti
antimony, in a cold or hot solution of a salt of that metal, does,
not acquire a metallic coating (ibid., Vol. XL, p. 465).
The electrolysis of antimonic acid and solutions of its salts
with electrodes of wood charcoal, or retort carbon, yields
stibio-mellogen, and with graphite electrodes stibio-graphitic
acid (Bartoli and Papasogli, Jour. Chtm. Soc., Vol. XLIV.,
1883, p. 592 ; The Electrician, Vol. XL, pp. 28 and 101).
A very good solution for obtaining the pure metal by the
separate current process, with an anode of antimony, is com-
posed of
Parts by weight.
Distilled water 12
Pure hydrochloric acid 1 -i-
Tartaric acid l"
Potassio tartrate of antimony 1
The electric current should be from about two Smee
elements, quite feeble, and of such a strength as to deposit a
thickness of metal not exceeding L \nd of an inch per week.
The metal thus deposited is hard, close-grained, of a slate-
grey colour, silky lustre, and of decided crystalline structure,
During deposition, when it has attained a thickness of y^th
of an inch, it sometimes cracks spontaneously, and becomes
curved in fantastic shapes, or if deposited on a thin metaj
Cathode it causes the latter to bend.
Electrolysis of Teroxide of Antimony. Sb0 3 . Molecular
weight = 168,. This compound, in a fused state, is reduced to
metal- by contact with charcoal.
(50)
Electrolysis of Terfluoride of Antimony. SbF 3 . Molecular
weight = 177. This is a very soluble salt, and," unlike the
chloride, is not at all decomposed by the addition to it of a
large quantity of water. By electrolysis with a separate
current of suitable strength, and an anode of antimony, it
slowly yields a thick layer of the pure hard grey metal.
By employing a dilute solution of the fluoride containing
free hydrofluoric acid, and using a current from two Smee
cells, or by passing a current from ten such cells through a
saturated neutral solution of the fluoride, during a long period
of time, I have obtained very beautiful collections of shining
grey crystals of the metal, which do not oxidise by exposure
to a'r.
Electrolysis of Terehloride of Antimony. SbCl 3 . Molecular
weight = 226*5. From a solution of this salt containing free^
hydrochloric acid, the antimony may be obtained by th'e
separate current process, and an antimony anode, either in the
form of the pure grey metal, or in that known as " amorphous "
or " explosive " antimony, according to the degree of density of
the current and the composition and temperature of the liquid.
The acidified aqueous solution of chloride of antimony is ah
excellent conductor of the current ; it dissolves an antimony
anode freely, yields plenty of the amorphous metal, and does
not deteriorate by use or by exposure to the atmosphere. It
is, however, decomposed with greater or less rapidity by con-
tact with zinc, cadmium, tin, lead, iron, brass, copper and
German silver, each of which deposits the metal upon itself
and dissolves. It is also decomposed by water, and therefore
articles wet with water must not be immersed in it, and those
taken from the liquid must be washed with dilute hydro-
chloric acid or a solution of tartaric acid previous to washing
them with water.
" Explosive Antimony." To obtain the explosive variety
of metal from the usual acidified solution, the current should
be of such a strength as to deposit not less than half a grain of
metal per square inch of cathode per hour. If the strength
is much- less, the kind of deposit suddenly changes to the grey
variety, sometimes preceded by formation of nodules of that
kind upon parts of the surface of the cathode. Thetwo kindis
of deposit do not adhere firmly to each other.
A good solution for yielding the u explosive " variety is
composed of one ounce of freshly precipitated teroxide or
oxychloride of antimony, dissolved in five or six ounces of pure
hydrochloric acid of specific gravity 1'12, or it may be made by
'saturating two volumes of the acid with the oxide or oxy-
chloride, and then adding one additional volume of the acid.
The oxide employed should not be that which has been made
by oxidising antimony with nitric acid, or with any mixture
( 56 )
containing that acid, nor should it be that which has long been
exposed to the air. A good solution may also be made by
mixing together two ounces of w-ter, four of hydrochloric
acid, and eight of finely powdered potassio tartrate of antimony
(i.e., tartar emetic). Either of these mixtures will bear a very
strong electric current without causing the deposition of a
black powder. It yields its metal rapidly, and coatings of any
desired thickness may be obtained. I have had some of quite
half an inch in thickness. Deposits of one-tenth of an inch
thick may be obtained from it in about seventy hours by
means of a current from two or three Smee elements.
A suitable depositing liquid may also be prepared by the
"battery process," i.e., by immersing a large anode of antimony
and a smaller cathode of platinum, silver, or copper in the
dilute acid, and passing a copious current until the metal is
freely deposited.
The explosive variety of deposit has quite a different appear-
ance from that of the other. It is highly smooth and lustrous,
and of a steel-black colour. Its appearance, however, varies
somewhat with the speed of deposition. It has the remarkable
property that if struck, broken, or rubbed, whilst at the
ordinary temperature, or if touched with a red-hot wire, it
suddenly rises in temperature, usually about 650F. ; the
amount of heat, however, varies with different circumstances.
Another difference between the pure variety of metal and the
explosive kind is that, when deposited upon a cathode of
mercury, the former is absorbed by and alloys with the mercury,
but the latter does not.
Like most electro-deposited metals, and especially the pure
variety of antimony, the outer and inner surfaces of deposits
of the explosive kind are in states of different cohesive strain,
which sometimes cause the deposit to crack spontaneously in
the depositing liquid and shatter to bits, evolving all its heat.
Faint crackling sounds not unfrequently issue from both
varieties of the depositing metals whilst forming in the liquids.
Sometimes, with a very dense solution of the chloride,
worked rapidly, and the liquid and cathode not at all
disturbed, a layer of deposited metal, in the shape of a large
button 1J inch diameter, gradually formed round the cathode,
just at the surface of the liquid.
A cylindrical bar of the explosive variety, about fths of an
inch in diameter, formed upon a rod of tin Jth of an inch
thick, when discharged by momentary contact of a heated
wire, instantly evolved sufficient heat to melt the tin com-
pletely, and the tin ran out and remained liquid a short time.
The change which takes place is propagated from particle to
particle of the mas*. By forming deposits of sufficient thick-
ness upon helices of stout copper wire, and discharging them
by application of heat to one end, the change was gradually
(57)
transmitted to the opposite end, and the velocity of its propa-
gation varied from 12 to 30 feet per minute, the velocity being
greater the thicker and more freshly formed and perfect the
deposit, and the weaker the cooling influences.
The temperature to which the deposit must be raised in
order to produce a sudden discharge varies according to several
circumstances, but is usually about 200 or 210F. in an air
bath ; the heat, however, of the substance begins to discharge
when the metal is heated to between 170 and 190F., and if
a piece of the substance is kept in water maintained at a
temperature of 190 to 200F. during one or two hours, it
gradually discharges the whole of its heat. By careful
manipulation, keeping one end of a rod of the substance hot
and the other cold, the former end only loses its singular
property. By carefully breaking thin pieces to small bits
between surfaces of wood in ice-cold water, and then tritu-
rating them very carefully under such water in a mortar, the
active metal may be obtained in a state of powder, with its
heat-giving power undiminished. The thermic property
gradually diminished by lapse of time, the powdered substance
losing it the most quickly ; that of a massive deposit disappears
in a period of one or two years.
The specific gravity of the pure crystalline variety of deposit
varied from 6 -369 to 6 -673, whilst that of the explosive kind
varied from 5-739 to 5-944. Their electro-chemical equivalents
also were different, and were determined by electrolysing their
solutions in a single undivided circuit with one of cupric
sulphate, and weighing the three deposits. I then found from
42-30 to 43-81 parts of the active kind, and 40-41 to 40-79
parts of the grey variety for each 31-7 parts of copper.
The discharge of heat in the explosive kind, whether sudden
or gradual, is attended by alterations of the substance. From
a bright black, highly lustrous surface, like that of iodine or
crystals of silicon, and a bright vitreous-looking fractured sur-
face, it changes to a dull grey earthy appearance and granular
fracture. Its cohesive power also changes ; and it acquires a
strongly acid taste.
As the sudden discharge was attended by evolution of an
acid fume (an effect of the heat), and the substance usually lost
about 3-5 per cent, in weight, consisting chiefly of chloride of
antimony, I made two analyses of the freshly-formed sub-
stance deposited from a pure solution of the chloride. The
following were the results :
No. 1. No. 2.
Sb 93-36 93 51
SbCl 3 5-98 ) ... 6-03 ) fi . 9 ,
HCI o-46 ; ( 0-21 (
99-80 99-75
(58)
It appears, therefore, that the deposit is a species of chemical
compound of the metal with the ingredients of the liquid ; and
that during the change its state of chemical union is destroyed.
R Bottger has stated (Chemisches Central Blatt, 1875, p. 674)
that the freshly deposited active metal contains occluded
hydrogen ; but this has been contradicted.
Smee appears to have been the first to deposit this variety of
antimony, but not to notice its singular property ; but since I
first observed it in October, 1854, several persons have redis-
covered it (see Comptes Rendus, Vol. LXXXIIL, pp. 854857;
also Dingl. Poly. Jour., Vol. 207, p. 427, and Jour. Chem. Soc. t
Vol. XI., p. 1,007).
A solution composed of the double chloride of antimony and
ammonium, with free hydrochloric acid, may be used instead
of that of the acidulated simple chloride for depositing the
metal, but possessess no very great advantages.
Electrolysis of Terbromide of Antimony. SbBr 3 . Mole-
oulur weight = 360. The electrolytic properties of a solution of
this salt are much like those of the chloride. It, however, less
readily yields a firm deposit of metal. A second variety of the
active substance was obtained from it in the following
manner: Dissolve one part by weight of freshly-made teroxide
of antimony in ten parts of aqueous hydrobromic acid of
specific gravity about 1-3. Filter the solution and electrolyse
it with an anode of antimony and a current from three Smee
cells, at a speed of deposition of about 4 grains of metal per*
Square inch of cathode per hour.
The deposits thus obtained were of a lighter colour than
those from the chloride, they were also quite dull in aspect,
and frequently perforated with holes all over the surface like a
sponge. This was caused by numerous bubbles of gas. The
deposit is less apt to spontaneously crack than the first variety;
it is also much more fragile and less hard. Its specific gravity
at GOT. is also much less, and varies from 5'415 to 5'472.
It contains a less percentage, viz., 79*52, of metallic antimony.
The residue consists of a colourless soft substance composed of
terbromide of the metal, and a little hydrobromic acid and
water.
It exhibited the same kind of thermic action as the first
kind, but the change did not spread throughout the mass
u-nless the substance was previously heated to about 250F.
By contact with a red-hot wire it then evolved all its heat
instantly with explosive violence, and with fracture and
dispersion of the substance. By gradually heating the entire
substance to about 320F.;it exploded suddenly.
In two pairs of experiments made to ascertain the electro-
chemical equivalent of this deposit I obtained 50'09 and 50-11,
also 51-2 and 51-4- parts for every 42-5 parts of the active
(59)
chloride variety deposited, or 32*2 parts of zinc consumed ia
the same circuit. Each of the quantities of the two kinds of
deposit contained about the same, viz., 40 parts, or Jrd of an
atomic weight of metallic antimony, the remainder being the
associated salt of the metal. These results indicate that in
each case the metal alone is deposited by the current, and that
during the act of deposition it occludes the saline matter, and
acquires the peculiar property.
Electrolysis of Teriodide of Antimony. SbI 3 . Molecular
weight 503. The solution employed was prepared as fol-
lows : Dissolve one part by weight of recently precipitated
teroxide of antimony in fifteen parts of aqueous hydriodic
acid of specific gravity 1'25. A current sufficiently strong was
passed through it, by means of an anode of antimony, to
deposit the metal at a rate not exceeding one grain weight per
square inch of cathode per hour. During the process the
tendency to evolution of hydrogen was so great as frequently
to completely disintegrate the deposit.
The substance thus obtained was dull in appearance, grey in
colour, scaly, extremely fragile, soft, and much less metallic
than even that obtained in the bromide solution. Its specific
gravity was 5 '27. On immersing it in water bubbles of gas
issued from all parts of its surface during a few seconds, and
produced a hissing sound like that of slaking lime. Pieces
one-ninth of an inch in thickness required to be heated to
33SF. before the contact of a red hot wire would cause them
to discharge their heat; they then discharged feebly and
evolved red vapours of antimonic iodide.
The unchanged substance yielded on analysis 7776 per ceni
of metal, the remainder being solid red iodide of antimony
and a little aqueous hydriodic acid. By depositing it slowly,
i.e., at the rate of '5 grain per square inch of cathode per hour,
in the same circuit as the chloride variety, its electro-chemical
equivalent was determined, and 48*07 parts were obtained for
every 42*5 parts of the other kind. The deficiency of equiva-
lent of metal consisted, no doubt, of deposited hydrogen.
For a more complete account of the several varieties of
electro-deposited antimony from the three salts see Phil. Trans.
Roy. Soc., 1857, 1858, and 1862; also Chem. News, Vol. VIIL,
pp. 257 and 281 ; and Jour. Chem. Soc.
Electrolysis of Tersulphide of Antimony. SbS 3 . Mole-
cular weight =21 8. This compound when in a fused state is
readily decomposed, and the antimony separated by char-
coal, and various metals, e.g., potassium, sodium, copper, tin,
iron, &c.
Electrolysis of Chlorides of Arsenic and Antimony. In
the electrolysis of the chlorides of arsenic and antimony some
arsenide and antimonide of hydrogen are produced at 'the
(CO)
cathode. If the three metals arsenic, antimony, and tin
are simultaneously present they are deposited in the order
given. From the solutions of the sulphides of those metals
in alkaline sulphides tin and antimony are deposited com-
pletely, and arsenic not quite completely, in the metallic state
<C. Luckow, Jour. Chem. Soc., Vol. XXXVIIL, 1880, p. 283).
Electrolysis of Antimoniate of Potassium. Bartoli and
Papasogli electrolysed an aqueous solution of this salt by
means of a current from eight Bunsen cells and an anode of
wood charcoal or gas carbon. Very much gas was evolved at
the cathode, and a small amount at the anode. The anode was
strongly attacked, and the electrolyte became deep black. The
authors found in the electrolyte a compound of carbon, hydro-
gen, oxygen, and antimony, which they term stibiomellogen
{Jour. Chem. Soc., Vol. XLIL, 1882, p. 406).
For the electro-chemical analysis of antimony compounds
see Jour. Chem. Soc., Vol. XLIL, 1882, p. 1,320; Chem. News,
Vol. XLVL, p. 106.
Separation of Bismuth. Bi. Atomic weight = 210. A
triad cation. Much less easily deposited in a coherent state
than antimony. By simple immersion tin coats itself with
very small shining plates of bismuth in a solution of ten grains
of nitrate of bismuth and a wineglassful of distilled water, to
which two drops of nitric acid have been added. Commaille
{Chem. News, Vol. XIV., p. 188) states that magnesium depo-
sits bismuth from solutions of its salts by simple immersion.
I have observed that it is also deposited from its aqueous
chloride by zinc, tin, lead and iron, but not by bismuth, anti-
mony, copper, brass, German silver, gold, or platinum.
Electrolysis of Oxide of Bismuth. Burckhard states that
fused oxide of bismuth is easily decomposed by a current from
twelve Bunsen cells with electrodes of copper; if platinum
wires are used, an easily fusible alloy of the two metals is
formed (Zeitschrift fiir Chemie, Vol. VI., p. 212). Melted oxide
of bismuth is instantly reduced to metal by contact with anti-
mony (H. Tamni, Chem. News, Vol. XXV., pp. 85-100).
Formation of Peroxide of Bismuth. Wernicke has pre-
pared this compound as a black deposit, having the composition
represented by BiO 2 , H 2 0, and a specific gravity of 5-571, by
-electrolysing by a current from two Daniell cells, with an
anode and cathode of sheet platinum, a solution of a mixture
of basic nitrate of bismuth and tartrate of sodium (Pogg.
Annalen, Vol. CXLL, p. 109).
Electrolysis of Nitrate of Bismuth. Sodium amalgam
decomposes a saturated solution of nitrate of bismuth, setting
free hydrogen and black powder of bismuth (Bottger). By
( the separate current process an anode of the metal, an ex-
( ci )
tremely feeble current, and a solution of the nitrate in water,,
with the minimum amount of free acid, to render it clear, I
have deposited the metal as a very beautiful but thin coating,
white, with a faintly pinkish tint, and a fine silky lustre..
According to some writers s ich a deposit is explosive.
Electrolysis of Fluoride of Bismuth. With pure dilute-
hydrofluoiic acid, a bismuth anode, and a current from a single
Since element, the conduction was extremely feeble, and only
a black film was deposited upon a copper cathode in thirty-
hours.
Electrolysis of Chloride and Iodide of Bismuth. Metallic
bismuth n,ay be deposited upon copper or brass, by means of
a current from a single Bun sen cell, from a solution composed
of 25 to 30 grammes of the double chloride of bismuth and
ammonium, dissolved in a litre of water, faintly acidified with,
hydrochloric acid. The deposit consists of a blackish mud,
with a film of bright adherent bismuth beneath (Bertrand,.
Athenaeum, April 22, 1876, p. 570 ; also Jour. Chem. Soc.,
Vol. L, 1876, p. 451). I have deposited the metal, evidently
containing some ingredients of the liquid, by a separate cur-
rent and a bismuth anode, from a solution of iodide of bismuth?
and iodide of potassium. The deposit was an extremely bulky,,
jet black powder, which contained iodine even after most per-
sistent washing, and became slowly oxidised by exposure to
the atmosphere.
A cyanide solution has also been recommended for depositing
bismuth, but an anode of that metal does not readily dissolve
in a hot solution of potassic cyanide.
One part of bismuth in 1,200,000 parts of mercury may b
detected by the addition of potassium amalgam and water, the
bismuth being electrolytically separated as a black powder on
the sides of the vessel (Serullas, Ann. Chem. et Phys. t 3rd Series,
Vol. XXXIV., p. 192).
For the electrolytic analysis of compounds of bismuth see
V. Francken, Chem. News, Vol. XL VI., p. 106 ; also Jour..CIiem.
Soc., Vol. XLIL, 1882, pp. 896 and 1,320.
Separation of Osmium. Os. Atomic weight = 199. A
cation. Zinc deposits osmium in the form of black flocks
when immersed in a solution of the black oxide in concen-
trated hydrochloric acid. Metallic mercury decomposes a
solution of osmic acid, and forms an amalgam of osmium and!
mercury (Tennant).
Smee electrolysed a solution of osmic acid (Os0 4 ), and ob-
tained a black deposit. Wohler passed a current from two
Bunsen cells by means of an anode of osmium through dilute
sulphuric acid ; the metal was freely converted into osmie
acid ; also through a solution of caustic soda the latter became-
(02 )
of a deep yellow colour, and a deposit of osmium was formed
upon the cathode (Chem. Neivs, Vol. XIX., p. 10).
Ruthenium. Eu. Atomic weight =104-2. A cation. No
reliable electrolytic experiments appear to have been made
with this metal. Its great rarity and infusibility, extreme
cost, and porous structure, are the chief obstacles.
Separation of Rhodium. Eo. Atomic weight = 104-3. A
cation. Smee stated that by means of a separate current from
ten of his cells, and platinum electrodes, he deposited this
metal from a solution of its sodio-chloride, and obtained a
brittle white deposit; and that with a stronger current the
deposit was a black powder.
Separation of Iridium. Ir. Atomic weight = 197. A cation.
Sodium amalgam decomposes a concentrated solution of sodio-
iridium chloride, and forms an amalgam of iridium. According
to F. Wohler, osmi-iridium is readily dissolved as an anode in
a solution of caustic soda. Smee stated that he had deposited
this metal in a bright reguline state on a small scale. Accord-
ing to a writer in Dingler's Polyteclmick Journal, both electro-
deposited iridium and rhodium detonate when heated (Jour.
Chem. Soc., 2nd Series, Vol. XL, p. 1,007), probably in conse-
quenc e of their containing hydrogen.
Separation of Palladium. Pd. Atomic weight =10G -5. A
cation. Mercury decomposes a solution of a palladium salt,
and forms an amalgam. According to S. Kern (Chem. Neivs,
Vol. XXXIIL, p. 236), the immersion of magnesium in aqueous
solutions of salts of palladium yields hydrogen, monoxide of
palladium, and hydrogenated palladium.
Formation of Peroxide of Palladium. Pd0 2 . Molecular
weight = 158-5. An anode of palladium, used to conduct a
current from two Bunsen elements into dilute sulphuric acid,
became slowly covered with an almost insoluble film of this
compound (F. Wohler, Chem. News, Vol. XIX., p. 10).
I passed a current from fifty Smee elements, by means of a
palladium anode and platinum cathode, through dilute sul-
phuric acid. No odour of ozone occurred at the anode, unless
the latter dipped but a very small depth into the liquid. Con-
duction was copious, and a deposit of splendid colour red,
purple, <fcc. formed upon the anode. By reversing the direc-
tion of the current the now well-known phenomenon of bend-
ing of the cathode by absorption of hydrogen took place ; and
by removing the charged cathode from the liquid and bending
it by mechanical means it evolved heat.
Electrolysis of Nitrate of Palladium. A solution of this
salt is said to be a good conductor, but apt to yield the metal
in the form of a black powder. I electrolysed strong nitric
( 63 )
acid, by means of a current from fifty Smee cells, with a
palladium anode and platinum cathode. Copious conduction,
and rapid decomposition of the acid, with abundant evolution
of red fumes, took place. Much gas was set free from the
anode, but none from the cathode until after a short time. The
anode was not at first visibly corroded, but after half an hour's
action the palladium slowly dissolved, forming a red liquid.
No metallic deposit formed upon the cathode.
Nitrate of palladium dissolved in water and acidified with a
little nitric acid, deposited upon the cathode a bronze coloured
coating, which by prolonged action became darker, and then
black, and was easily soluble in nitric acid. Some reddish
oxide was formed upon the anode. Alkaline solutions behaved
similarly, except that the action was slower, and the deposited
metal more adhesive (Schucht. Berg und Hiittenmannische
Zeitung, Chem. News, Vol. XLL, p. 280).
Formation of Fluoride of Palladium. PdF 4 , Molecular
weight = 182-5. I electrolysed thirty per cent, pure aqueous
hydrofluoric acid, with a sheet palladium anode, in a large
platinum vessel as the cathode, by means of a current from
six Smee elements. Free conduction occurred, and much gas
was evolved from each electrode, and there was a strong odour
of ozone. A dark, red-brown, thin coating for medupon the
palladium, but did not dissolve during fifteen hours' electro-
lysis. The liquid was filled with minute floating particles of
palladium, caused by the reducing action of the hydrogen from
the cathode. After six days' continuous action the anode was
greatly corroded.
I also electrolysed the pure anhydrous acid in a chilled state,
in the same vessel, with a thick palladium anode and the same
current, and sometimes with a current from thirty cells. The
process was difficult and very dangerous, and notwithstanding
the low temperature, and that the vessel was closely covered
by a lid of paraffin, the acid volatilised rapidly and fumed
greatly, partly in consequence of the escaping hydrogen and
the heat of conduction resistance. The coldness of the vessel
and the intense attraction of the acid for moisture caused
water to condense upon the lid of the vessel, and rendered it
difficult to preserve the acid in the anhydrous state. The
lid was therefore made to overhang the edge of the cup, and
was also covered by a layer of cotton wool. With a current
from twenty cells the conduction was copious. The anode
quickly became coated with a thick, dark, red-brown, brittle
crust, which was of a redder colour on the side next the anode,
and did not perceptibly impede the passage of the current.
This crust was scraped off at intervals of about one hour into
a platinum dish standing upon a slab of iron heated to about
350F., and at once transferred to a closed platinum bottle.
After eleven hours' action, the acid was still colourless, as if
the crust upon the anode was perfectly insoluble. Some black
powder, which proved to be metallic palladium, was, however,
found upon the cathode, and indicated that some palladium
had dissolved and been reduced. The crust also on the side
towards the anode was nearly black when dry, and showed
signs of metallic particles when pressed between smooth
surfaces of agate, indicating some reduction by the diffused
hydrogen.
In some other experiments the hydrogen was more perfectly
excluded from touching the anode. The platinum cup was
2J inches wide and 3J inches deep, divided into two equal
parts by a weU-fitting vertical plate of paraffin, which extended
to within half an inch of the bottom. The palladium anode
and platinum cathode were each about 4 inches long and
1 inch wide, and firmly fixed in slits in the two halves of the
paraffin lid. With 5^ ounces of the perfectly anhydrous acid,
and a current from twelve one-pint Grove cells, the conduction
was copious, and in five minutes the immersed part of the
anode had acquired a deep brown colour. The electrolysis
was continued during five hours, the anode being taken out
and scraped each half hour, and the crust preserved in a
platinum bottle. The crust was hard, and sparks were some-
times caused by particles of it being decomposed by the heat
of friction in removing it. A hissing sound was heard during
the whole of the electrolysis, but the density of the fumes
prevented any effervescence being seen. 10*46 grains of black
powder were found upon the cathode and adjacent parts of the
vessel and partition, and yielded lO'll grains of metallic
palladium ; this indicated some small degree of solubility of
the crust, and the great necessity of excluding hydrogen from
touching the anode. The anode had lost 3 7 '90 grains in
weight, and 54*13 grains of the dry brown crust was obtained.
After deducting the lO'll grains of palladium found in the
liquid, the remaining quantity of corroded metal would form
only 47'62 grains of tetrafluoride ; the crust therefore contained
in addition probably some hydrofluoric acid.
I also found that a palladium anode was very rapidly cor-
roded by the passage of a current from six Grove elements
through pure potassic fluoride in a state of fusion. Finely
divided palladium was found in the saline residue.
Electrolysis of Chloride and Iodide of Palladium. I
electrolysed concentrated, also dilute hydrochloric acid, by a
current from fifty Smee cells with a palladium anode and a
platinum cathode. Action was instant and rapid, hydrogen
was copiously evolved from the cathode and chlorine from the
anode, and the anode dissolved, forming a blood-red liquid, and
a black deposit of palladium soon formed upon the cathode.
(05)
M. A. Bertrand recommends a perfectly neutral solution of
the double chlorides of palladium and ammonium, with or
without the use of a separate current, for the separation of
this metal (Chem. News, Vol. XXIV., p. 227). It is stated
that with a separate current from two or three cells and a pal-
ladium anode, the current is somewhat impeded in this solu-
tion by a bright golden yellow coating forming upon the anode.
Iodide of palladium dissolved in a solution of potassic iodide
is an unsatisfactory one for yielding reguline metal.
Electrolysis of Cyanide of Palladium. Pd.Cy 2 . Mole-
cular weight = 158*5. A solution of the double cyanide of pal-
ladium and potassium, containing free potassic cyanide, is said
to yield by the separate current process thick deposits of the
metal in a reguline state. The liquid holds in solution a large
quantity of the metal, and may be prepared either by the
usual chemical means i.e., by dissolving cyanide of palladium
in a solution of potassic cyanide, or by the battery process.
A less satisfactory mixture may also be made by dissolving
chloride of palladium in a solution of the alkaline cyanide. A
solution for depositing palladium is prepared as follows :
Cyanide of palladium is mixed with 7 per cent, of ferro-
cyanide of pDtassium, 3 per cent, of caustic potash, and 60
per cent, of water, and the mixture boiled during half an
hour, the lost water being replaced (Frantz, Chem. Centr.,
1876, p. 592).
Separation of Platinum. Pt. Atomic weight = 197. A
tetrad cation. Nearly all electrolytic operations with platinum
are performed with a solution of the tetrachloride, or with
hydrochloric acid, because, with the exception of anhydrous
hydrofluoric acid, a solution which yields chlorine at the
anode is nearly the only one in which metallic platinum will
dissolve; even a solution of potassic cyanide with a strong
current corrodes an anode of platinum but sparingly. Nearly
all the ordinary metals become coated with platinum in its
solutions by the process of simple immersion, and it may be
separated by each of the methods of electrolysis.
Magnesium in a solution of platinic chloride evolves
hydrogen, and after about twenty hours deposits a black
powder of metallic platinum. On leaving it in contact with
water a brown hydrate of platinum is formed (S. Kern, Jour.
Chem. Soc., 1876, Part I., p. 684). Sodium amalgam decom-
poses a concentrated solution of platinic chloride, also one of
chloroplatinate of ammonium, and forms in each case an
amalgam. According to Joule, the electro-deposition of
platinum with a cathode of mercury produces an amalgam of
the two metals. I observed that by simple immersion of
arsenic, antimony, tellurium, bismuth, zinc, cadmium, tin, lead,
iron, cobalt, nickel, copper, brass, German silver, mercury, or
t
( 66 )
silver in a solution of tetrachloride of platinum, they became
coated with that metal. According to Lan, a solution of one
part of platinic chloride in 15 parts of alcohol and 50 of ether
deposits platinum on tin, brass, and white metal (Jour. Cliem.
Soc., Vol. XLIL, 1882, p. 1,145). Bottger adds carbonate of
sodium to platinic chloride as long as carbonic anhydride is
evolved, then a little starch sugar, and, finally, chloride of
sodium till the precipitated platinum appears white. The
resulting solution coats articles by simple immersion (Watts's
"Dictionary of Chemistry," Vol. VI., p. 950).
One of the best liquids for obtaining thick reguline deposits
by the separate current process is that of Roseleur, who pre-
pared it as follows : Convert 10 parts of platinum into dry
tetrachloride, and dissolve it in 500 parts of distilled water
(the whole should dissolve). Add, with stirring, to the solu-
tion 100 parts of crystallised phosphate of ammonia previously
dissolved in 500 parts of distilled water ; and as this produces
a precipitate, add at once, with copious stirring, a ready-made
.solution of 500 parts of crystalline phosphate of soda in 1,000
parts of distilled water. Boil the mixture until an odour of
ammonia ceases and the liquid begins to turn blue litmus
paper red. The liquid must be used hot, and a strong cur-
rent must be employed, because an anode of platinum does
not dissolve in it. It is decomposed by, and deposits platinum
upon, zinc, tin, or lead by simple contact. A solution made
by dissolving tetrachloride of platinum in one of potassic
cyanide has also been used for the same purpose, but it also
does not dissolve a platinum anode.
Formation of Tetrafluoride of Platinum. In some ex
periments of mine a platinum anode in water, containing 10
per cent, of pure anhydrous hydrofluoric acid, was not corroded
by the passage of a current from six Smee or six Grove
elements during many hours. Very free conduction occurred,
a powerful odour of ozone and a gas which inflamed a red-hot
splint were evolved at the anode, but no platinum was de-
posited. With an aqueous solution of pure potassic fluoride
precisely similar effects occurred.
A current from 24 elements of magnesium and platinum in
an exciting solution of common salt was passed during 18
hours, by means of platinum electrodes, through water con-
taining 40 per cent, of the same pure acid, but no corrosion of
the anode took place. With a current from ten Smee cells
and platinum electrodes I also electrolysed water containing
80 per cent, of the pure acid. Abundant conduction with
evolution of hydrogen and ozone occurred ; the anode lost
16-58 grains by corrosion during 36 hours, and became covered
with a brownish black crust, which partly dissolved in the
liquid to a brownish solution. No platinum was deposited,
(67)
probably because the hydrogen decomposed the solution. I
also electrolysed with platinum electrodes the pure anhydrous
acid in a precisely similar way to that described under
" Fluoride of Palladium." With a current from forty Smee
cells the anode corroded rapidly, and acquired a dark red
brown crust, which was insoluble in the acid, but rapidly
deliquesced in the air; it dissolved, with partial decomposi-
tion, to a basic salt and formation of a blood-red liquid, in
water.
By electrolysis with platinum electrodes, during 16 hours,
of water containing 40 per cent, of the pure acid, mixed with
its own bulk of strong nitric acid, gases were freely evolved ;
but scarcely any platinum was dissolved, and none was de-
posited. With an equal bulk of strong hydrochloric acid
substituted for the nitric, hydrogen and chlorine were set
free, but in four hours' action the anode was very little
corroded. With the same volume of sulphuric instead of the
nitric acid, after many hours' action, the anode was again but
little corroded. With phosphoric anhydride dissolved in the
dilute hydrofluoric acid, and the mixture electrolysed, the
results were similar. And with much selenious acid dissolved
in it, selenium containing traces of platinum was freely de-
posited, and gas was evolved as before (see Phil. Trans. Roy.
Soc. t 1869, p. 200).
By electrolysing fused fluoride of potassium or lithium with
platinum electrodes, the anode was rapidly dissolved, and the.
resulting salt of platinum instantly decomposed, and its metal
set free; and by electrolysing pure double fluoride of hydrogen
and potassium in a fused condition, the platinum anode was
rapidly dissolved, and a colour imparted to the salt. Fused
silico-fluoride of potassium, or the fused fluorides of silver,
copper, lead, manganese, or uranium, when electrolysed by
a current from six Smee cells, did not corrode a platinum
anode.
Electrolysis of Tetraehloride of Platinum. Pt. C1 4 .
Molecular weight = 339. This salt may be formed by the
electrolysis of hydrochloric acid with a platinum anode and a.
dense current. According to Commaille (Chem. News, Vol.
XIV., p. 188) magnesium deposits pure platinum from a solu-
tion of platinic chloride. I have observed that crystals of
silicon did not acquire a coating of platinum in that liquid.
A smooth deposit of platinum upon bright copper may be
obtained by immersing the copper in a boiling solution com-
posed of 100 parts of distilled water, 12 of caustic soda (or 40
of sodic carbonate), and 10 of platinic chloride. Copper arid
brass may also be coated by means of contact with zinc in a
solution prepared as follows : To a solution of platinic chloride
add sodic carbonate in fine powder until effervescence ceases,
F 2
( CS)
then add some glucose, and afterwards as much sodic chloride
as will produce a white precipitate. The solution should be
used at a temperature of 60C. (" Les Mondes," Chem. News,
Vol. XIX., p. 226).
Separation of Gold. Au. Atomic weight = 196-6. A triad
cation. Like platinum, gold is very easily separated from its
solutions by each of the methods of electrolysis. Thallium
deposits gold from its solutions (W. C. Reid, Chem. News, Vol.
XII., p. 242). Auric terchloride and the auro-cyanide of
potassium are the only common soluble salts of the metal ; a
solution of the oxide in hydrobromic acid, or of the aurate
of ammonia (a very explosive substance) in potassic cyanide
previously dissolved in water, may also be employed. A gold
anode is corroded and dissolved in various liquids, e.g., hydro-
chloric acid, solution of sodic chloride, c. Runspaden has
observed that a gold anode in dilute sulphuric acid is con-
siderably oxidised, and a definite hydrated oxide of gold is
formed (Chem. News, Vol. XX., p. 179). By immersing zinc
in a solution of sulphide of gold dissolved in one of sulphide
of ammonium, excluded from the atmosphere, it becomes
coated with gold (C. D. Braun, Chem. News, Vol. XXIX.,
p. 230).
J. Schiel has produced Nobili's rings on a horizontal plate of
burnished gold used as the anode in very dilute nitric acid, the
negative pole being a platinum wire, supported a short distance
above the gold plate. After passing a current of suitable
strength during about ten minutes, the plate was washed,
dried, and exposed a few hours to sunlight ; the rings then
appeared of brilliant colours. With an alkaline solution the
effects were less powerful (Pogg. Ann. CLIX., p. 493).
Under the influence of an electric current nitric acid dis-
solves gold (Berthelot, Jour. Chem.Soc., Vol. XXXVIIL, 1880,
p. 158).
Formation of Fluoride of Gold. By electrolysing pure
dilute hydrofluoric acid with a gold anode, in a platinum
crucible as the cathode, by means of a current from six Sraee
cells, during many hours, the current passed very freely, much
gas came from each electrode, and an odour of ozone from the
anode. The anode gradually became covered with an insoluble
red-brown film. None of the metal dissolved. Similar effects
occurred with more concentrated acid, and with a very much
stronger current. The red-brown film appeared to be gold ;
it was insoluble in nitric acid, and when burnished with agate
it appeared like gold.
With a gold anode in pure anhydrous hydrofluoric acid, at
10F., even a current from forty Smee cells was but feebly
transmitted. In one and a-half hour the anode acquired a
dark, reddish-brown film, with a few crystals, at first of a
(CO)
greenish colour, upon its edges. By exposure to the air the
crystals became first yellow and then red. A current from
six Smee cells was conducted freely by a gold anode, in a
solution of pure fluoride of ammonium containing free ammonia.
The anode evolved much gas, and became covered with an
insoluble, bright, lemon-coloured powder, but no gold appeared
on the cathode. By means of a current from three and also
from six Grove elements I electrolysed with a gold anode the
pure fluorides of potassium and lithium in a melted state.
Metallic gold separated, and the anode was very rapidly
corroded.
Electrolysis of Auric Terehloride. Au.Cl 3 . Molecular
weight = 303*1. Sodium amalgam easily reduces a solution
of auric terchloride, and, according to G. A. Koenig, even char-
coal reduces it to metal by simple immersion (Journal of the
Franklin Institute, May, 1882; see also Chem. News, Vol.
XLIV., p. 215). The mere contact of magnesium, phosphorus,
arsenic, antimony, tellurium, bismuth, palladium, silver,
mercury, copper, and nearly all the base and brittle metals,
with this solution separates the metal. I have noticed that
crystals of silicon did not reduce it, but that by contact of
amylene, " petroleum ether," benzine, coal gas, and numerous
liquid hydrocarbons, with the aqueous solution, films of the
metal gradually separated (see Proc. Birm. Phil. Soc., Vol. IV.,
Part L).
According to D. Tommasi, solution of auric chloride is not
reduced to metal by hydrogen or platinum alone, but only by
hydrogen in the presence of platinum (Chem. News, Vol. XLL,
p. 116).
Electrolysis of Auro-Cyanide of Potassium. KCy.AuCy.
Molecular weight = 287 7. In a solution of the double cyanide
of gold and potassium, zinc, copper, brass, and German silver,
became gilded by simple immersion ; but platinum, gold, silver,
nickel, iron, lead, tin, bismuth, and antimony did not.
This salt, when dissolved in a suitable proportion of water,
and a certain proportion of potassic cyanide added, constitutes
the ordinary electro-gilding solution. The compound may
either be formed by dissolving the salts in water, or by taking
a solution of potassic cyanide, and electrolysing it with an
anode of gold and a cathode of platinum, until gold is freely
deposited. This process, however, leaves a large excess ^ of
simple potassic cyanide in the liquid, and also by abstracting
some of the cyanogen to form auric cyanide, and substituting
oxygen in its stead, it introduces caustic potash, and the
caustic alkali gradually becomes carbonate by absorbing car-
bonic acid from the atmosphere. The solution, when formed,
yields by electrolysis gold at the cathode, whilst cyanide of
gold is formed at the anode, and dissolves.
( 70 )
For deposition of gold by an electric current in solution of
potassic ferrocyanide and auric chloride, see E. Ebermayer,
Jour. Cliem. Spc., Vol. XXXIV., 1878, p. 178. For a solution
suitable fcr gilding iron, see Watts's "Dictionary of Chemistry,"
Vol. VIII., Part II., p. 1,119. A great variety of mixtures,
containing auric chloride or cyanide, and other substance?,
such as the carbonates and chlorides of potassium and sodium,
sodic bisulphate, phosphate, and pyrophosphate, potassic ferro-
cyanide, and sulphocyanide, aqueous ammonia, carbonate of
ammonium, &c., have been employed for electro-gilding. The
particulars of their composition maybe found in "The Art
of Electro-Metallurgy," Longmans and Co.'s " Text Books of
Science."
By electrolysing a solution of methylamine with a gold
anode and a feeble current during several days I obtained no
deposit of gold.
Separation of Silver. Ag. Atomic weight =108. A
monad cation. Its commonest soluble salts are the nitrate,
acetate, argento-potassic cyanide, ammonio-nitrate, and am-
monio-chloride. Other soluble ones are ammonio carbonate,
sodio hyposulphite, argento-potassic iodide, potassio-tartrate,
and argento-potassic sulphocyanide. Sulphate of silver is but
slightly soluble. All the solutions of silver are readily decom-
posed by an electric current with deposition of metal upon the
cathode, and in some cases with oxidation of the silver of the
liquid at the anode, and formation of argentic peroxide.
Nearly all the solutions of the salts of silver are reduced to
metal by simple immersion in them of any of the base metals.
Aluminium reduces the silver from an ammoniacal solution of
argentic chromate (Watta's " Dictionary of Chemistry," Vol.
VII., p. 54). According to Tribe, silver deposited by copper
always contains copper, if the solution has absorbed air (Chem.
News, Vol. XXIV., p. 7G). Gold in contact with silver in a
cold or hot acid or neutral solution of a salt of silver receives
no deposit of silver (Raoult, Jour. Chem. Soc., Vol. XL, p. 465).
Formation of Silver Peroxide. F. Wohler states that if
a current from two Bunsen cells is passed through a dilute
solution of sodic sulphate or dilute sulphuric acid, by means of a
silver anode, the latter becomes coated with argentic peroxide,
due to the action of ozone. With a solution of potassic nitrate
similarly treated, brown argentic oxide is formed ; with one
of potassic ferrocyanide the anode becomes coated with white
amorphous argentic ferrocyanide, and with one of potassic
bichromate it becomes covered with reddish-black crystallised
argentic chromate (Chem. News, Vol. XVIII., p. 189). Brester
states that by electrolysing melted caustic soda, with an anode
of silver, the anode dissolved and silver was deposited on the
platinum cathode, and that on cleansing the cathode with
nitric acid, a residue of black powder of platinum was obtained
(Chem. Neivs, Vol. XVIII., p. 14$). I have on various occa-
sions noticed a similar residue after electrolysing melted
argentic fluoride with platinum electrodes.
Electrolysis of Argentic Nitrate. Ag.N0 3 . Molecular
weight = 170. According to Brester, hydrogen, evolved
either by electrolysis, by the decomposition of steam by red-
hot iron, or by zinc or iron in dilute sulphuric acid, reduces a
solution of argentic nitrate, but not one of the sulphate; also, if
a cathode of platinum, whilst being used in the electrolysis of
dilute sulphuric acid, be instantly dipped into a solution of the
nitrate, it sometimes reduces the silver and sometimes not
(Chem. News, Vol. XVIII., p. 144). Eussel observed that pure
hydrogen reduces a solution of the nitrate to metal and nitrite
(Watts's "Dictionary of Chemistry," Vol. VIIL, Part II.,
p. 1,070).
Sodium amalgam decomposes a strong solution of argentic
nitrate, and forms an amalgam of silver and mercury. Joule
formed the same amalgam, but richer in silver, by depositing
silver from the same solution into a cathode of mercury.
According to W. C. Keid, thallium deposits silver from a solu-
tion of its nitrate by simple immersion (Chem. News, Vol. XII.,
p. 242). Metallic mercury, in an acidified and moderately
strong solution of the same salt, forms a "silver tree " or
"Arbor Dianas." I observed that an aqueous solution of
argentic nitrate yielded its metal by simple immersion to
arsenic, antimony, bismuth, mercury, copper, brass, German
silver, nickel, iron, lead, tin, cadmium, and zinc, but not to
silver, gold, or platinum. In an alcoholic solution of the salt,
antimony, bismuth, zinc, tin, copper, brass, and the alloys of
silver with zinc, tin, or lead, deposited silver by simple immer-
sion, but iron did not.
Electro-deposited nickel does not separate silver by simple
immersion from a solution of argentic nitrate (J. Spiller, Chem.
News, Vol. XXIV., p. 175). Aluminium after six hours' im-
mersion begins to precipitate the silver, either from slightly
acid or neutral solutions, whether concentrated or dilute (A.
ossa, Watts's "Dictionary of Chemistry," 2nd Supplement,
p. 54). According to S. Kern, magnesium precipitates oxide
of silver from an aqueous solution of argentic nitrate (Chem.
News, Vol. XXXIL, p. 309).
Fused argentic nitrate, when electrotysed by a separate
current, yields silver at the cathode and a large amount of
oxygen at the anode.
Formation of Argentic Peroxide. Ritter, in 1814, dis-
covered that when a concentrated solution of argentic nitrate
is electrolysed with two thick platinum wires as electrodes
(72)
peroxide of silver, Ag 2 2 , is deposited in crystals upon the-
anode, and metallic silver upon the cathode. Fischer states
that these crystals always contain argentic nitrate (Watts's-
" Dictionary of Chemistry, Vol. V., p. 303). I have also found
a nitrogen compound in them.
To deposit coherent silver from a solution of the nitra f e
requires the liquid to be weak and the current feeble. Accord-
ing to Luckow, the formation of peroxide of silver at the anode
in a solution of argentic nitrate may be prevented by the
addition of glycerine, milk, sugar, or tartaric acid (Chem. News,
Vol. XLIL, p. 76).
Berthelot obtained sesquioxide of silver by the electrolysis
of a 10 per cent, solution of argentic nitrate. It was in the-
form of large, thick, black, lamillar, striated needle?, of bril*-
liant metallic lustre (Jour. Chem. tioc., Vol. XXXVIIL, 1880 r
p. 442).
Electrolysis of Argentic Fluoride. Ag.F. Molecular
weight =127. I have observed that carbon and crystalline
boron do not separate silver from fused argentic fluoride at a
red heat, but that crystals of silicon thrown upon the melted
salt become red hot, and burn vividly, producing silicic
fluoride and separating silver ; also that hydrogen separates
silver from the semi-fluid salt. In an aqueous solution of the
salt, crystals of boron did not separate silver, but crystals of
silicon deposited slowly crystals of silver. Stannous fluoride
in contact with platinum also separated silver from such a
solution. I observed also that in a mixture of solutions of
argentic fluoride, hydrofluoric and nitric acids, crystals of
silicon evolved spontaneously inflammable bubbles of silicide
of hydrogen gas (Chem. News, Vol. XX., p. 28, and XXIV.,
p. 291).
I found the following to be the chcmico-electric order of
various elementary substances in fused argentic fluoride, the
first being the most positive : Silver, platinum, charcoal of
lignum vitse, palladium, gold. And in a dilute aqueous solu-
tion of the salt, aluminium, magnesium, silicon, iiidium,
rhodium, and carbon of lignum vitae, platinum, silver, paK
ladium, tellurium, gold (Chem. News, Vol. XXL, p. 28).
In a number of experiments of electrolysing argentic*
fluoride in a fused state in a covered platinum vessel with
platinum electrode?, with a current from six Smee cells, con-
duction commenced before the salt had fused, and when the
salt had become quite liquid the conduction appeared to be as
perfect as when the electrodes were united by a wire. Xo
signs of genuine electrolysis were observable in either case. I
also electrolysed the fused salt by a current from ten Smee
cells, with an anode of highly ignited charcoal of lignum vitoe.
Very little conduction took place ; the anode was, however,
(73)
corroded, and evolved gas (Phil. Trans. Roy. Soc., 1870, p. 234 ;
Chem. News, Vol. XXL, p. 28).
I also electrolysed pure anhydrous hydrofluoric acid in a
chilled state by means of a silver anode and a current from
ten Smee cells. Conduction was free, the anode corroded
rapidly, and became covered, first with some black powder
upon its edges, probably peroxide, and then with a grey
powder, probably silver, which contained only a trace of
soluble silver salt.
By electrolysing a saturated neutral aqueous solution of
argentic fluoride, with a small platinum anode and a large
platinum cathode, by a current from six Grove cells, the con-
duction was free, but no gas or odour was evolved. A thick,
hard, and strongly adherent crust of argentic peroxide formed
upon the anode. By using a more dilute solution a similar
crust was formed, and gas was evolved from the anode. An
aqueous solution of this very soluble salt was decomposed by
an extremely feeble current with great ease. The deposition
of silver, also, with this solution was so rapid that the deposit-
ing vessel soon became largely occupied by a loose, bulky mass
of fibrous crystals of silver, which soon metallically united the
two electrodes if not frequently prevented.
In the electrolysis of solutions of argentic fluoride contain-
ing free hydrofluoric acid, with silver anodes, I repeatedly
observed that after the current has passed some time the
anode becomes extremely brittle and porous, and its surface
crumbles away, and falls as a powder to the bottom of the
vessel, instead of dissolving smoothly, as with silver, in a solu-
tion of potassic cyanide. In order to test whether free fluorine
diffused into the metal, I employed as an anode a pure silver
tube, closed at the bottom, and communicating at the top with
a pressure gauge. No signs of gas or of free fluorine were,
however, observed by means of this test, or by chemical ones.
Electrolysis of Argentic Chloride. Ag.Cl. Molecular
weight= 143 '5. Aluminium evolves great heat by contact
with melted argentic chloride, and separates the silver in
melted globules. It also precipitates silver as a fine crystalline
powder from an ammoniacal solution of the chloride (A. Cossa,
Watts's "Dictionary of Chemistry," Vol. VI, p. 54). Fused
argentic chloride is resolved by the current into silver at the
cathode and chlorine at the anode (Faraday). Sodium
amalgam reduces the chloride, bromide, and iodide of silver,
when in contact with water.
Electrolysis of Argentic Chlorate. Ag.CIo 3 . Molecular
weight = 191 '5. A solution of this salt containing free chloric
acid was easily decomposed by a current from two Smee cells,
with a silver anode. It yielded a copious deposit of loose
silver upon the cathode, and upon the anode a black crust,
( 74 )
apparently of argentic peroxide, which soon stopped the cur-
rent. To electrolyse ifc properly requires a feeble current, a
large cathode, and a very large anode (see Proc. Birm. Phil.
oc. 9 Vol. IV., Part I.).
Electrolysis of Silver Perehlorate. A solution of argentic
perchlorate, containing free perchloric acid, with a silver
anode, is a remarkably good conductor. It conducted copiously
a current from a single Smee element, and was decomposed
even more readily than the chlorate. The anode was rapidly
corroded, and acquired first a thick loose coating of black
solid matter, and then one of a dark green colour. To elec-
trolyse this liquid properly requires a very feeble current, a
rather small anode, and a very large cathode (see Proc. JJirm.
Phil Soc., Vol. IV., Part I.).
Electrolysis of Argento-sodie Sulphite. An aqueous
solution of this salt is said by Koseleur to possess a singular
property. When a piece of metal is immersed in a solution of
another one, in which it coats itself with that metal, a portion
of the immersed one dissolves, and produces an immense num-
ber of minute electric currents which pass from an infinity of
minute portions of the surface of the metal into the liquid,
decomposing it, and re-enter at other minute portions of the
metallic surfaces, and deposit an equivalent weight of the
other metal as a coating upon the immersed one ; but in this
particular solution a spontaneous chemical change also occurs
in the liquid itself, the sulphurous anhydride of the argentic
sulphite takes oxygen to itself to form sulphuric anhydride,
and sets the silver free, and this silver adheres to any solid
surfaces present, i.e., to the immersed metal, and to the con-
taining vessel. The sulphuric anhydride unites with some of
the soda of the undecomposed portion of the sulphite, and
liberates sulphurous anhydride, and forms sulphate and bi-
sulphite of sodium. This action is very similar to that which
takes place in certain processes of coating looking-glasses with
pure silver.
A solution also composed of sulphite of silver dissolved
in an aqueous solution of potassic sulphite has been used for
depositing silver b\ r the separate current process. It is a very
good one except that it gradually decomposes and deposits its
silver by the influence of light. A solution has also been
formed by dissolving argentic chloride in an aqueous solution
of sodic hyposulphite. It easily yields its metal by electro-
lysis with a current, but under the influence of light it is
decomposed, and its silver precipitated as argentic sulphite.
Electrolysis of Argentic Sulphate. Ag.S0 4 . Molecular
weight = 204. In an aqueous solution of the sulphate of
silver, antimony, tin, iron, copper, and the alloys of silver
( 75;.)
with zinc, tin, or lead, deposited the silver by simple immer-
, sion, but bismuth did not.
Electrolysis of Argento-potassie Cyanide. Ag.Cy.KCy.
Molecular weight = 1991. A solution of this salt, containing
an excess of potassic cyanide, constitutes the ordinary silver-
' plating liquid. It may be formed by dissolving the salt in
water, say one or two ounces per gallon the exact propor-
tion is not material and then adding about one-tenth of
. its weight of potassic cyanide. Nearly the same mixture is
obtained by electrolysing a solution of potassic cyanide with a
silver anode, until silver is freely deposited ; in this case,
however, caustic potash is formed in the liquid, and gradually
becomes converted into carbonate by contact with the air.
Electrolysis of the solution yields silver alone at the cathode,
and at the anode argentic cyanide, which dissolves. A num-
ber of modifications of this liquid have been employed, such
as solutions formed by dissolving nitrate, chloride, or ferro-
cyanide of silver in one of potassic cyanide, but the above
mixture is the best.
By dissolving some bisulphide of carbon in a strong solu-
tion of potassic cyanide, and adding a very minute proportion of
this solution occasionally to the above mixture, the physical
character of the deposited silver is greatly changed ; instead
of being soft and somewhat dull white in appearance, it
becomes hard and highly lustrous, like burnished metal. I
have found by chemical analysis that it contains a minute
proportion of sulphur.
By electrolysing a 33 per cent, aqueous solution of methy-
lamine with a silver anode and a feeble current from a single
Smee cell, the anode slowly dissolved, and a loose deposit of
silver crystals formed upon the cathode. Somewhat similar
results were obtained with a strong solution of trimethylamine.
Blagden states that the desilvering of lead is facilitated by
dissolving about half a per cent, of zinc in the refined metal
at 540C., and passing a voltaic current through it by means
of copper wires, until all the zinc has risen to the surface !
This crust contains the silver, and may be removed after the
melted mass has fallen to 450. The process must be
repeated several times.
For a solution fit for silvering iron, see Watts's " Dictionary
of Chemistry," Vol. VIII., Part II., p. 1,119. For deposition
of silver from a pasty mixture of salts by simple contact, see
Koseleur, Jour. Chem. Soc., Vol. XXXIV., 1878, p. 538. For
the electrolytic analysis of silver, see Chem. News, Vol. XLIL,
p. 331 and p. 76 ; Watts's "Dictionary of Chemistry," Vol.
VII, p. 790; Jour. Chem. Soc., Vol. XXXVIIL, 1880, p. 747.
Separation of Mercury. Hg. Atomic weight = 200. A
dyad cation. I have observed that solutions of -mercurous
( 70)
salts have their metal deposited by simple immersion, by
arsenic, antimony, bismuth, zinc, cadmium, tin, lead, iron,
copper, brass, and the alloys of silver with zinc, tin, lead, or
copper. Iron deposited mercury from a solution of mercury
acetate. A. Cossa states that aluminium deposits mercury by
simple immersion in aqueous solutions of mercuric nitrate,
chloride, and cyanide ; also from a solution of mercuric
chloride in alcohol, and of mercuric iodide in one of potassic
iodide (Watts's " Dictionary of Chemistry," Vol. VII., p. 54).
Thallium deposits mercury from an aqueous solution of
mercurous sulphate (W. C. Reid, C/iem. News, Vol. XII.,
p. 242). Solutions of salts of mercury have been electrolysed
by the mutual contact of two metals in them (see Gladstone
and Tribe's experiments, Phil. Mag., 4th series, Vol. XLIX.,
p. 245).
I have observed that by passing a current from a mercury
anode through dilute sulphuric acid into a platinum cathode
the latter soon acquires a coating of mercury. E. Obach
states that a liquid alloy of sodium and mercury showed no
signs of electrolysis by passing through it an electric current.
Electrolysis of Nitrate of Mercury. Copper immersed
in a solution of nitrate of mercury deposits the latter, and
forms an amalgam. By electrolysing a solution of cupric
sulphate into a cathode of mercury a similar alloy is formed.
An aqueous solution of mercuric nitrate has been used by
electro-platers for "quicking" the surfaces of articles pre-
vious to plating them. A solution of nitrate of mercury
yields its metal to bismuth, zinc, cadmium, lead, iron, or
copper, but not to silver, gold, or platinum, by simple immer-
sion.
Electrolysis of Mercuric Chloride. Hg.Cl 2 . Moleular
weight = 271. From an aqueous solution of this salt mag-
nesium deposits mercuric oxide and calomel (Commaille, Cliem.
News, Vol. XIV., p. 188).
A solution of mercuric chloride, slightly acidulated with
sulphuric acid, in a platinum vessel cathode, was electrolysed,
and the amount of mercury in it determined by means of a
current from six Bunsen cells, the anode being a sheet of
platinum. Mercurous chloride was first deposited, but at the
end of one hour all the salt was reduced to mercury so per-
fectly that the supernatant liquid was not rendered cloudy by
addition of ammonia. By running a stream of water finally
through the vessel whilst the current was passing the whole
of the mercury was obtained in a pure state (F. "VV. Clarke,
Report of the Chemical Society of Berlin, No. 12, 1878). Gladstone
and Tribe noticed that when a weak current was passed
through a solution of mercuric chloride into a cathode of
platinum a film of mercurous chloride was deposited, but if
the current was strong, metallic mercury was set free.
Electrolysis of Potassio Mercuric Cyanide. 2KCy.Hg.
Cy 2 . Molecular weight = 382 -2. The solution of this salt
readily deposits its metal by simple immersion upon copper,
and various of the base and alkali metals, and is therefore
used by electro-depositors to prepare, by the process termed
" quicking," the surfaces of metal articles to receive an adherent
deposit of silver. It also readily yields its metal by means of
the other methods of electrolysis.
Electrolytic Movements of Mercury. In consequence of
being a liquid, mercury exhibits certain peculiar phenomena of
motion and alteration of form when used as an electrode.
This effect appears to be partly a consequence of a film of
oxide or other salt formed upon it when it is an anode, and of
hydrogen or other substance formed upon it when a cathode,
and partly also of simple electrification. H. Herwig has
observed that a drop of mercury placed on a glass plate, and
strongly electrified by either pole of a Holtz machine, becomes
flattened, and if the mercury is in a narrow glass tube its capil-
lary depression is greatly diminished. The effect is greatest
with the positive pole, probably in consequence of the higher
tension of that pole (Pogq. Ann. CLIX , pp. 489492). As
early as the year 1801, Gerboin noticed some of the electrolytic
movements of the metal, and the phenomena have since been
investigated by Sir H. Davy, Sir J. Herschel, Serullas, Erman,
Runge, Poggendorff, Gmelin, and others (see Gmelin's " Hand-
book of Chemistry," Vol. L, pp. 381384). Also by T.
8. Wright (Phil Mag., Vol. XIX., I860, pp. 129133), by R.
Sabine (Phil. Mag. [5], Vol. II., p. 401), and Th. du Moncel
<Watts's "Dictionary of Chemistry," Vol. VIII., Part I., p. 714).
The movements have also been applied by Lippmann to the
measurement of extremely feeble electric polarities in his
capillary electroscope ; and also to the production of motion
in his capillary electric engine. In most of these cases the
electrolyte employed was dilute sulphuric acid.
Electrolytic Sounds. By employing as an electrolyte a
solution of potassio mercuric cyanide, with electrodes of the
liquid metal, I discovered that the mercury emitted electrolytic
sounds, and became covered on its surface with minute waves,
symmetrically disposed, and beautiful in appearance. These
waves and sounds appear to be due to the rapid alternate for-
mation and destruction of films upon the mercury by electro-
lytic action. The best solution for producing it consists of 10
grains of mercuric cyanide and 100 of pure potassic hydrate
dissolved in 2J ounces of aqueous hydrocyanic acid of
"Scheele's strength," and the liquid filtered. The waves and
sound occur at the cathode. The mercury may be contained,
in two small watch glasses submerged in the solution contained
in a large, flat-bottomed glass basin. The current employed
may be from two Grove or five Smee element?, and con-
veyed into the electrodes by platinum wires protected from
the electrolyte by means of glass tubes. By suitable tests I
found that during the emission of the 'sounds the electric
current was rendered to a considerable extent intermittent,
and that the arrangement might be employed for similar uses
to those of a voltaic break-hammer; the intermittence, how-
ever, is much less perfect (see Proc. Roy. Soc., 1861 and 1862).
For the detection and estimation of mercury by electrolysis,
see F. W. Clarke, Jour. Chem. Soc., Vol. XXXIV., 1878, p. 916 ;
also Vol. XXXVL, 1879, p. 976 ; J. Lefort, ilid.,'Vo\. XXXVIIL,
1880, p. 510 ; Watts's "Dictionary of Chemistry," Vol. VIIL>
Part II., p. 1,277. J. B. Hannay estimates mercury electroly-
tically by passing a current through a solution of its sulphate
into a platinum dish containing it.
Separation of Copper. Cu. Atomic weight = 63 5. A dyad
cation. By simple immersion of magnesium in a solution of
cupric chloride, Brunswick green, but no metallic copper,
appears; but in one of cupric sulphate, the metal, together
with its hydrated protoxide, and a green subsalt are produced
(Commaille, Chem. News, Vol. XIV., p. 188). From a solution
of cupric nitrate or sulphate, aluminium after two days'
immersion deposits copper ; in the nitrate solution a green
basic salt of copper is also produced ; but if a minute amount
of alkali chloride is added to either of these liquids, depo-
sition commences at once. From a solution of cupric chloride
or acetate, aluminium separates copper at once, but the
deposition afterwards proceeds slowly (A. Cossa, AVatts's
"Dictionary of Chemistry," Vol. VIL, p. 54). According to
Smee iron does not decompose a neutral solution of cupric
acetate, nor alkaline ones of ammonuret, ammonio nitrate, or
ammonio sulphate of copper, but decomposes one of the nitrate.
Zinc amalgam deposits copper from neutral solutions of cupric
salts, and forms a copper amalgam (Damour, Jour. Prac.
Chem., Vol. XVII., p. 345). By adding crystals of silicon to
melted protoxide of copper, I observed that sudden incan-
descence and a full white heat were produced, and metallic
copper was separated. Thallium deposits copper from the
solution of cupric nitrate, sulphate, and acetate (W. C. Reid,
Chem. News, Vol. XIL, p. 242). Raoult states that gold in
contact with copper, in either a cold or boiling acid or neutral
solution of a cupric salt, receives no deposit of copper (Jour.
Chem. Soc., Vol. XL, p. 465).
Smee states that the use of solutions of the hyposulphite,
ammoniuret, or acetate of copper, with a separate current,
(79)
offers no advantages for depositing copper, because they are
difficult to decompose, and require a current from several cells,
that a copper anode is but little corroded in a solution of
sulphocyanide of potassium, and the solution does not hold
much dissolved metal; also that the anode is very slightly
acted upon in a solution of tartrate of potassium. M. P.
Schutzenberger found from five to ten per cent, of cuprous
oxide in copper electro-deposited from an acetate solution ( J.
B. Mackintosh, Chem. Neivs, Vol. XLIV., p. 279, and Vol.
XLV., p. 101).
Formation of Nitride of Copper. By passing a current
from six Grove cells into one end of a solution of sal am-
moniac contained in a long glass trough by means of a copper
anode, and out of the liquid at the distant end by a platinum
sheet cathode, the liquid becomes blue, and a heavy solid
nitride of copper of a chocolate colour collects at the cathode
(Grove, Phil. Mag., 3rd Series, Vol. XIX., p. 100).
Electrolysis of Cuprie Nitrate. Cu.2No 3 . Molecular
weight = 187 '5. I observed that a solution of cupric nitrate
yielded its metal to zinc, tin, lead, or iron, by simple immer-
sion, but not to nickel, copper, silver, gold, platinum, or anti-
mony. J. B. Mackintosh states that in the electro-deposition
of copper from a nitrate or sulphate solution containing citric
or tartaric acid, the deposited metal is not pure. With the
nitrate solution containing citric acid, electrolysis was attended
by a strong odour of hydrocyanic acid (Chem. News, Vol.
XLIV., p. 279, and Vol. XLV., p. 101).
Electrolysis of Cuprie Fluoride. Cu.F 2 . Molecular weight
= 101-5. I observed that copper was separated from its
melted fluoride by adding fragments of magnesium ; also that
crystals of silicon immersed in a solution of the fluoride evolved
gas, and became instantly coated with copper.
By means of a separate current from six Smee cells, a
platinum wire helix anode and a copper wire helix cathode, I
electrolysed fluoride of copper, fused at a bright red heat in a
deep copper cup. Conduction was copious, as if the salt was
a metal, and an acid vapour was evolved. The anode was un-
altered, no copper was deposited, but the cathode had lost
3-35 grains in weight by corrosion near the surface of the
melted salt ; the copper vessel was also similarly acted upon
in several experiments and caused to leak. The phenomena
were much like those obtained with melted argentic fluoride.
A solution of cupric fluoride in pure dilute hydrofluoric acid,
with copper electrodes, conducted freely the current from a
single Smee element, and yielded a good deposit of copper.
Electrolysis of Cuprie Chloride. Cu.Cl 2 . Molecular
weight = 134-4. Aluminium acts briskly on a solution of
( 80 )
capric chloride at 16C, setting free copper, hydrogen, and
aluminium oxychloride, the composition of which varies with
the temperature (D. Tommasi, Jour. Chern. Soc., Vol. XLIL,
1882, p. 1,266; Vol. XL1V., 1883, p. 19; Chem. News, Vol.
XLVL, p. 62). Copper is at once deposited from its chloride,
and more slowly from its acetate, by aluminium (A. Cossa,
Watts's " Dictionary of Chemistry," Vol. VII., pp. 54 and 383).
I observed that in a solution of cupric chloride, bismuth, zinc,
tin, lead, and iron deposited copper by simple immersion,
but nickel, copper, silver, gold, platinum, or antimony did not ;
also that in a solution of sub-chloride of copper in strong
aqueous ammonia zinc received a deposit of copper by simple
immersion, but tin, lead, iron, nickel, copper, silver, gold,
platinum, bismuth, or antimony did not. When a copper
platinum couple is immersed in a dilute solution of this salt
insoluble white cupreous chloride is deposited on both the
metals. With couples formed of zinc-platinum or magnesium-
platinum the action is stronger, and metallic copper is deposited
upon the platinum (Gladstone and Tribe, Phil. Mag. y 4th
Series, Vol. XLIX., p. 425).
M. Weis Kopp coats iron with copper by simply immersing
it in a bath composed of 10 parts of cupric chloride, 10 of
nitric acid, and 80 of hydrochloric acid of specific gravity
1-105 (Chem. News, Vol. XXL, p. 47). According to O.
Gaudain, articles of cast iron, wrought iron, or steel may be
coated with copper by dipping them into a melted mixture of
fluoride and chloride of copper, with five or six parts of cryolite,
and a little basic chloride, in a plumbago crucible (Jour. Chem.
Soc., Vol. XL, p. 955). In some cases, copper is extracted
from sandstone, which contains it in small proportion, by dis-
solving the ore out by dilute hydrochloric acid, and immersing
pieces of scrap iron in the liquid until they are wholly dis-
solved, and metallic copper is left.
When a feeble electric current is passed by means of copper
electrodes through a solution of chloride of copper in dilute
hydrochloric acid, the anode becomes covered with snow-white
crystals of cupreous chloride, and the cathode with a thick de-
posit of loose copper (Chem. Neivs, Vol. XXII., p. 167). If a solu-
tion of cupric chloride was electrolysed by a feeble current with
platinum electrodes, chlorine appeared at the anode and
cupreous chloride at the cathode ; but if the current was strong,
metallic copper was also deposited upon the edges of the cathode
(Gladstone and Tribe). Smee states that a solution of this salt
is less readily decomposed by an electric current than one of the
nitrate, but more readily than one of the sulphate, that it is
also one of the worst liquids for the electrolytic separation of
metallic copper, and that the deposited metal is apt to assume
.a very peculiar appearance. He also states that a solution of
the ammonio-chloride is a bad one, having a tendency to
(81 )
evolve hydrogen and yield a spongy copper deposit ; and that
one composed of iodide of copper dissolved in aqueous solu-
tion of potassic iodide cannot be employed because it liberates
iodine. The electrolysis of solution of cupric bromide docs
not appear to have been examined.
Electrolysis of Cuprie Sulphate. Cu.SO^. Molecular
weight =127'5. I have noticed that a solution of cupric
sulphate gave up its metal by simple immersion of zinc, tin,
lead, or iron, but not to nickel, copper, silver, gold, platinum,
bismuth, or antimony. One of the oldest facts in electro-
chemistry is the deposition of copper upon iron by immersing
the latter in an aqueous solution of cupric sulphate. Vase
numbers of steel pens, iron wire, and other small articles of
steel and iron are coated with copper by means of the same
liquid slightly acidulated. For coating iron wire in this way
Koseleur used a mixture composed of one part of cupric sul-
phate and one of sulphuric acid dissolved in from 50 to 100
parts of water. To coat brass with copper, Dr. C. Puscher
dissolves 10 parts of cupric sulphate and 5 of ammonic
chloride in 150 of water; dips the clean articles in the liquid
for one minute, drains them, and then heats them over a char-
coal fire until the ammoniacal salt is expelled, and then
washes and dries them (Chem. Neu-s, Vol. XXIII., p. 215).
According to M. Soret, clean copper dissolves in a boiling,
saturated, aqueous solution of neutral cupric sulphate, and is
deposited in a metallic state on cooling the liquid (Annal. de
Chimie, Vol. XLIL, 1854, pp. 257 277). I have found only a
small quantity of red suboxide of copper separate under these
conditions. According to Wurtz, pure cupreous hydride
can be obtained by the electrolysis of a dilute solution of
copper sulphate (Jour. Chem. Soc. t Vol. XXXVIIL, 1880,
p. 299).
Cupric sulphate resulting from the oxidation of cupric
sulphide in the earth exists in the water of many mines.
Immense quantities of such sulphide are also roasted with
common salt to oxidise and render soluble the cupriferous
mineral, which is then dissolved out by dilute hydrochloric
acid, and the copper in each of these cases is extracted from
the liquid by immersing in it scraps of iron. The copper
collects as a red powder consisting of small feathery crystals
at the bottom of the vats after all the iron has dissolved.
Great quantities of the metal are annually deposited in this
manner.
Copper is sometimes deposited upon iron by the influence
of the contact of a second metal. M. Fred. Wiels uses the
following liquid: Dissolve 150 parts of sodio-potassic tartrate,
80 of soda lime containing from 50 to GO per cent, of caustic
soda, and 35 of cupric sulphate, in 1,000 parts of water. By
o
(82)
immersing clean articles of iron or steel in contact with a
piece of zinc or lead in this liquid a sufficiently long period of
time they receive a strongly adherent coating of copper, of any
desired thickness. Pure tin in contact with zinc in this
liquid does not become coppered, but oxidises, and its oxide
gradually precipitates as red suboxide all the copper of the
solution.
Copper is also deposited by means of the contact of two
different metals in two different liquids (the " single cell pro-
cess ") for the purpose of coating cast-iron cylinders for calico
printing (see Chem. News, Vol. XXX., p. 219 ; also Jour. Chem.
Sue., Vol. XIII., p. 196).
A good solution for depositing by means of a separate
current is composed of four parts of crystallised cupric sul-
phate (Cu.S0 4 , 5H 2 0) and one of sulphuric acid, in 18 or 20
of water. Sometimes sulphate of zinc or of potassium is added
to such a solution in order to improve the deposit.
According to A. Long, copper electro-deposited by a
separate current from a solution of its sulphate contains
minute amounts of hydrogen, carbonic oxide, carbonic anhy-
dride, and water (Watts's "Dictionary of Chemistry," Vol.
VII, p. 383).
Elimination of Impurities from Copper by means of
Electrolysis. Very few metals are likely to be electro-
deposited along with copper from the usual acid sulphate
depositing solution by a separate current ; the most likely one
is cadmium. In the electrolysis of that solution with an
anode of ordinary copper, a considerable amount of black
insoluble matter separates at the anode. An analysis of
this substance by Max Duke of Leuchtenberg gave the fol-
lowing :
Tin 33-50
Oxygen 24 '82
Copper 9*24
Antimony 9'22
Arsenic 7 '20
Silver 4 '45
Sulphur 2-46
Nickel 2-26
Silicia 1'90
Selenium T27
Gold -98
Cobalt -86
Vanadium '64
Platinum '44
Iron '30
Lead -15 = 99'69
(Erdmann, Jour. Prac. Chem., Vol. XLV., pp. 460468.)
The following are comparatively recent analyses kindly sup-
plied to me by a friend. They are those of the powder from
( S3 )
copper plates used as anodes in depositing copper on statues,
Ac. :
No. I.
Copper
85*50
No. II.
. 27-70
No. III.
67-90
"Water and oxy
\Vater and oxy
Sulphur
1810
4-950
sen ..
. 21-05
Iron
5-55
Arsenic
2 480
Copper .
19-40
Insoluble earthy
Silver
1-815
Antimony
. 7-35
matter
3-40
Sulphuric acid
1150
Sulphur . ...
. 6-55
Organic matter..
2-25
insoluble eaitln
Silver
5 -61
205
matter
950
Arsenic
5-20
Silver
55
Antimony
750
Ewthy matter
4-35
Loss
20
Iron
750
Bismuth
. 1'25
Bismuth
650
Chlorine
. -70
Alumina
250
Iron
60
Chlorine
250
Nickel
20
-Gold
085
Organic matter.
20
Lead
050
Gold
01
020
03
100-000
100-00
:
oo to
Refining of Crude Copper by Electrolysis. This pro-
cess is carried out on a large scale by Messrs. Elkington, at
their copper works, Pembrey, South Wale?. The process
simply consists in making large slabs of the crude metal,
obtained by the ordinary smelting process, anodes in the usual
oupric sulphate solution, and passing currents from numerous
dynamo electric machines through the solutions, until the
slabs are wholly dissolved and their copper deposited. Each
current passes in an undivided state through a series of such
electrodes and solutions in order to diminish the cost of the
process.
The impurities which separate vary, of course, with the
different samples of crude metal. In the process, oxygen,
sulphur, selenium, carbon, boron, silicon, and arsenic are not
deposited at the cathode. Silver is precipitated at the anode
by the traces of hydrochloric acid present in the common
sulphuric acid employed. Gold falls as metal at the anode,
lead as sulphate ; carbon and metallic sulphides, also selenium
and silica, fall at the anode. Zinc, iron, tin, cadmium, cobalt,
nickel, and antimony are more or less dissolved, but, being
less readily deposited than copper, remain in solution. Arsenic
falls as an arsenide, and the metal most likely to be deposited,
viz., cadmium, is present so rarely, or in so small an amount,
as to remain in solution.
Eleetrie Etching 1 , &e. Copper being a very suitable metal
for the purposes of engravers and printers, the electric corro-
sion of anodes in a solution of cupric sulphate was soon applied
to engraving and etching. Copper being also a metal easily
deposited, the process of electro-deposition of copper in solu-
tions of its sulphate was also applied to the multiplication of
G 2
( 84 )
engraved plates, the copying of set-up type, the manufacture
of works of art, and even of colossal statues, &c. The details
of these and other technical uses of electro-chemical action
may be found described in works on Electro-Metallurgy.
For the uses of electrolysis in the metallurgy of copper by
the processes of Becquerel, Keith, and Patera, see Jour. Chem.
Soc. t Vol. XXXVI, 1879, p. 760; also Bias and Miest, Chem..
News, Vol. XLVI , p. 121. The latter also apply electrolysis
to all kinds of ores.
Electrolysis of Cuproso Potassic Cyanide. There are-
several cuproso cyanides of potassium. The one usually
employed for electro-deposition is formed by dissolving green
cuproso cupric cyanide to the point of saturation in a solution
of potassic cyanide, and then adding some more of the potassic
solution, and using the mixture at a temperature of about
150F. The base metals much less readily deposit copper
by simple immersion in this liquid than in the ordinary cupric
sulphate solution. By the passage of a separate current this
salt is also less readily decomposed than cupric sulphate, and
hydrogen is freely set free at the cathode along with the
copper.
Various mixtures of salts containing potassic cyanide have
been employed fcr depositing copper upon base metals.
Koseleur recommends the following : Rub 20 parts of crystal-
lised verdigris to powder in a little water, add to it with stir-
ring 20 parts of washing soda dissolved in 200 parts of water,
mix the solution with one of 20 parts of bi-sulphite of sodium
dissolved in 200 parts of water, and add the mixture with
stirring to a solution of 20 parts of pure potassic cyanide dis-
solved in COO parts of water ; then if the mixture is not colour-
less, add more potassic cyanide until it is so. It may be used
either hot or cold. A second one he recommends is composed
of 20 parts of strong aqueous ammonia, 30 of sodic bi-sulphite,
35 of cupric acetate, 50 of potassic cyanide of 70 per cent.,
and 2,500 of water. The ammonia and copper salt are dis-
solved in one portion of the water, and the cyanide and bi-
sulphite in the other, and the two solutions mixed. If the
resulting solution is at all blue, more potassic cyanide must be
added to render it colourless. This mixture also may be used
hot or cold.
Another liquid employed for the same purpose may be made
by dissolving 40 parts of the blue ammoniuret of copper and
80 parts of potassic cyanide in about 1,000 parts of water.
W. H. AValenn recommends cyanide of copper dissolved to
saturation in an aqueous solution of equal parts of potassic
cyanide and ammonium tartrate, and sufficient oxide and
ammoniuret of copper added to prevent evolution of hydrogen,
at the cathode when the liquid is used at 80C. with a current
(85 )
from a single Smee element. Dr. Eisner used, a solution
composed of one part cf potassic bitartrate boiled in ten paits
of water, and as much freshly-prepared and wet hyd rated
<rapric carbonate which has been washed with cold water,
stirred with it, as the liquid will dissolve. A small quantity
of potassic carbonate is then added. He states that a copper
anode dissolves rfadily in this mixture.
According to F. Weil, by employing an alkaline solution in
which cyanides are replaced by organic acids or glycerol,
copper may be firmly deposited by a separate current on
wrought iron, cast iron, and steel, and the acids or glycerol
are not decomposed (Jour. Chem. Soc., Vol. XLIL, 1882,
p. G70).
Copper has been deposited upon iron by the combined
action of simple immersion and of a separate current in a
solution cf one part of cupric oxalate and a large excess of
potassic bi- or quad-oxalate in ten to fifteen parts of water
<Watts's "Dictionary of Chemistry," Vol. VIIL, Part II.,
p. 1,118).
The physical properties of the copper deposited from the
various mixture*, and from each solution at different tempera-
tures, or by different strengths of current, vary considerably.
A trace of carbonic bisulphide in the cupric sulphate solution
makes the deposit brittle, the anode also becomes black, but if
there is also a great excess of acid, it sometimes becomes very
bright ; and if the liquid also contains much potassic sulphate,
the deposited copper is said to be bright. The deposit also
from the cyanide is usually bright when the current is strong,
and of a dull aspect when it is wcik. According to Favre,
electro-deposited copper contains more heat than the rolled
metal (Watts's "Dictionary of Chemistry," Vol. VII., p. 462).
For the absorption of gases by deposited copper, see Watts'a
"Dictionary of Chemistry," Vol. VIL, p. 383.
Analysis of Copper Ores by Means of Electrolysis. As
this series of articles is not of a technical character very few
remarks are admissible on this subject. To carry out als3 pro-
cesses of electrolytic analysis successfully, requires a knowledge
of analytical chemistr}', because the methods in nearly all
cases (with other metals as well as with copper) are combina-
tions of ordinary chemical and electro-chemical actions.
By electrolysis all the copper is separated from solutions
containing free hydrochloric acid on the addition of ammonium
or sodium chlorides, or sodium acetate ; similarly from solu-
tions containing excess of ammonia, ammonium carbonate, or
potasjic cyanide. From a solution containing mercury, s'lver,
bismuth, and copper, the last two metals are only deposited
after the greater portion of the first two has separated (C.
Luckow, Jour. Chem. Soc., Vol. XXXVIIL, 1880, p. 283).
The electrolytic determination of the amount of copper pre-
sent in a liquid is more readily made than that of almost any
other metal, and this agrees with the usually extreme degree
of purity of the deposited substance. The last traces of
copper may also be perfectly precipitated in a coherent state
from a solution of blue vitriol containing two platinum elec-
trodes, by a current of suitable strength. The deposited
copper, however, is not perfectly pure if tartaric or
citric acid is present. The electrolytic process is exten-
sively used. Details of it may be found in Watts's "Dic-
tionary of Chemistry," Vol. VII., pp. 384, 790 ; Vol. VIII.,
p. 559: Cliem. News, Vol. XIX., 1869, p. 221 ; XXIV., pp. 100
and 172; XLL, pp. 25, 213; XLIL, p. 331; XLIV., 1881,
p. 279 ; XLV, 1882, p. 101, and XL VI., p. 105 : Jour. Chem.
Soc., 1876, Part II., p. 115; 1877, Part I., p.340 ; Vol. XXXVL,
1879, p. 276; Vol. XXXVIII., 1880, pp. 282 and 583; VoL
XL., 1881, p. 1,081 ; Vol. XLIL, 1882, pp. 428, 660, 896,
and 1,320.
Separation of Nickel. Xi. Atomic weight = 59. A dyad
cation. Less readily deposited than copper. From slightly
acid solution of salts of protoxide of nickel, magnesium de-
posits by simple immersion metallic nickel and hydrogen
(Roussin, Chem. News, Vol. XIV., p. 27). Zinc amalgam
deposits nickel from neutral solutions of nickel salts by simple
immersion, and forms an amalgam (Damour, Jour. Prac. Chem.,
XVII., p. 345).
By contact with a second metal, nickel is also in some cases
deposited from its solutions. Stolba takes a boiling hot, one-
third saturated solution of chloride of zinc, in a copper vessel,
renders it clear by adding just sufficient hydrochloric acid,
then adds a few particles of zinc, sufficient to cause a slight
deposit of zinc upon the copper. He next adds either chloride
or sulphate of nickel, until the mixture is distinctly green.
The metals to be coated, viz., cast iron, wrought iron,
steel, brass, or copper, are then immersed in the boiling solu-
tion in contact with zinc until they are coated (Watts's " Dic-
tionary of Chemistry," Vol. VII., p. 850 ; also Chem. News,.
Vol. XXXV., p. 166). C. Mene coats either iron, steel, zinc,
lead, copper, or brass with nickel, by immersing it in a boil-
ing hot neutral solution of chloride of zinc, containing frag-
ments of nickel. If the liquid is acid, the deposit appears
dull (Chem. News, Vol. XXV., p. 214). A nickel-gold couple
produces no deposit of nickel in acid or neutral, hot or cold, solu-
tions of salts of nickel (Raoult, Jour. Chem. Soc., Vol. XL, p. 646).
An aqueous solution of cream of tartar and hydrated nickel
oxide, with a little soda, gave by the separate current process
peroxide of nickel at the anode (Wernicke, Watts's u Dictionary
of Chemistry," Vol. VII., p. 899).
(87)
Electrolysis of Nitrate of Nickel. Ni.2N0 3 . Molecular
weight = 183. Nickel may be deposited by a separate current
from a solution formed by dissolving one part of nitrate of
nickel in one part of strong aqueous ammonia, and then adding
20 to 30 times its volume of aqueous bisulphate of sodium of
specific gravity 1*999 (Roseleur). I have always found that
when nickel solutions contained nitrates the deposited metal
was of a bad colour.
In France a solution is prepared by dissolving four parts of
nickel nitrate in four parts of aqueous ammonia and 150 parts
of water holding in solution 50 parts of acid sodium sulphite.
A very feeble current is used (Boden, Watts's " Dictionary
of Chemistry," Vol. VIIL, Part II., p. 1,388).
Electrolysis of Fluoride of Nickel. By immersing crys-
tals of silicon in an aqueous solution of nickel fluoride, con-
taining free hydrofluoric acid, I observed that they did not,
become coated with metal ; but by heating the crystals with
ten times their weight of nickel fluoride to redness in a porce-
lain crucible, vivid incandescence occurred, and nickel was
deposited and melted by the great heat evolved.
Electrolysis of Chloride of Nickel. Ni.Cl 2 . Molecular
weight = 130. The simple immersion of copper in a solu-
tion of the double chloride of nickel and sodium is suffi-
cient to deposit the nickel (Becquerel, The Chemist, Vol. V.,
p. 408). Zinc throws down the metal from a solution of
nickel chloride previously rendered alkaline by addition of
ammonia.
One of the first really good liquids for depositing nickel by
means of a separate current for practical purposes appears to have
had its origin in the following experiments published by me :
" I have deposited nickel in the state of reguline white metal
from a solution of the double chloride of nickel and ammo-
nium, by making a lump of metallic nickel the anode in a
strong aqueous solution of hydrochlorate of ammonium (sal
ammoniac), and passing a strong current until the liquid
acquired a pale greenish-blue colour" (Pharm. Jour., Vol. XV.,
No. 9, September 1, 1855, pp. 106 and 131). T. Fearn, in
1872, published the composition of a solution for depositing
nickel, viz., 24 parts of sal ammoniac dissolved in 160 parts of
water, and the liquid then saturated with protoxide of nickel
at 120F.
Martin and Dalmotte dissolve 1,250 grammes of citric acid,
500 of sal ammoniac (or ammonium sulphate) and 500 of
nitrate of ammonium in 1 5 litres of water ; heat the liquid to
80C., and saturate it with recently precipitated hydrate of
nickel, then add 2 J litres of aqueous ammonia ; dilute to 25
litres, and after cooling add 500 grammes of ammonic car-
(88)
bonate, subside the mixture, and filter the liquid. Us3 the
solution at 50C. (Watts's "Dictionary of Chemistry," Vol.
VIII., Part II., p. 1,388).
Electrolysis of Sulphate of Nickel. Ni.SO^. Molecular
weight = 155. Magnesium deposits nickel by simple immer-
sion from a solution of nickel sulphate (Commaille, Chem. News,
Vol. XIV., p. 188). Zinc throws down the metal perfectly
from a solution of nickel sulphate rendered alkaline by addi-
tion of ammonia (A. Merry, Jour. Chem. Soc., Vol. XIII. ,
p. 311).
The best solution for electro-depositing nickel is made either
by dissolving the crystallised double sulphate of nickel and
ammonium, in the proportion of half a pound to a pound, in a
gallon of water, or the double chloride of nickel and ammo-
nium may be used instead. A large anode of nickel should
be employed. Bottger states that the best solution for de-
positing nickel by means of a separate current is made by
adding to crystals of proto-sulphate of nickel as much liquid
ammonia as is necessary to dissolve them (Pharm. Jour., Vol.
III., 1843, p. 358). Nagel dissolves two parts by weight of
crystals of sulphate of nickel in a mixture of six parts of
aqueous ammonia of specific gravity '909 and thirty parts of
water, and uses the mixture at a temperature of about 100F.
Another liquid is composed of 100 parts of sulphate of nickel,
53 of tartaric acid, and 14 of hydrate of potassium, dissolved
in a suitable proportion of water. It is said tD yield a bright
deposit of metal. Some recipes include nitrate of ammonium,
or nitric acid, which is objectionable (see also A. C. and E.
Becquerel, Comptes Rendus, Vol. LV., p. 18 ; also Kavser,
Jour. Chem. Soc., Vol. XXXIV., 1878, p. 537).
Another nickel solution is composed of 87 -5 parts of nickel
sulphate, 20 of ammonium sulphate, 17*5 of citric acid, and 2
litres of water (Hesse, Watts's "Dictionary of Chemistry,"
Vol. VIII., Pait II., pp. 1,118 and 1,388).
More recently nickel-sulphate-depositing solutions contain-
ing borax have been employed. I analysed one, and found it
to contain sulphate and chloride of nickel, borax, and a small
quantity of ammonia. A Mr. Powell, of Cincinnati, adds 1 oz. to
loz. of benzoic or pyrogallic acid to each gallon of the ordinary
nickel plating solution " to improve it."
A solution of ferrocyanide of nickel dissolved in aqueous
potassic cyanide has also been employed for depositing the
metal.
In the deposition of nickel from the solution of the double
sulphate of nickel and ammonium with a cast nickel anode
the anode disintegrates to a loose powder upon its surface, and
also by solution of the nickel a loose coating of impurity accu-
mulates upon it, and falls to the bottom of the liquid and col-
( 80 )
lects as a yellow mud. The following are the results of a
chemical analysis of the yellow substance :
Hydrated oxide of nickel 52 7
80 3 (chiefly insoluble basic sulphates) 11-5
Moisture 11-3
Sesquioxide of iron 9-4
Sand (with particles of graphite) 86
Metallic nickel 4-3
Oxide of copper -7
990
Also a trace of sulphur, but no silver, lead, or zinc, nor any
metallic iron.
Electrolysis of Selenate of Nickel. By adding to a solu-
tion of neutral selenate of nickel aqueous ammonia until the
liquid was of a clear blue colour, and electrolysing with a
nickel anode and a current from three Smee cell?, I obtained
a brilliant and very white deposit of the metal.
Electrolytic Analysis of Nickel Compounds. See Chem.
News, Vol. XXIV., pp. 100 and 172 ; Vol. XXVL, p. 209
Vol. XXXVIIL, p. 26 ; Vol. XLL, p. 25 ; Vol. XLIL, pp. 75
and 331 ; Vol. XLVI. p. 105. Jour. Chem. Soc., 1876, Part II.,
p. 115; Vol. XL, p. 204, Part L, 1877, p. 340, and Part II.,
pp. 924 and 925; Vol. XXXIV., 1878, p. 537; Vol. XXXVIIL,
1880, pp. 284, 583, 751, and 771 ; Vol. XL., 1881, p. 1,081 ;
Vol. XLIL, pp. 896, 1,320 ; Vol. XLVL, p. 105. Watts's
"Dictionary of Chemistry," Vol. VII., pp. 791, 849.
Separation of Cobalt. Co. Electro-chemical equivalent
59
= 2 9 -5. A dyad cation. Magnesium deposits metallic cobalt
2
and hydrogen from slightly acid solutions of protoxide of
cobalt (Roussin, Chem. News, Vol. XIV., p. 27). Thallium
deposits a basic salt by simple immersion in a solution of
nitrate of cobalt (W. C. Reid, Chem. News, Vol. XII., p. 242).
Zinc amalgam deposits cobalt by simple immersion in neutral
solutions of salts of cobalt, and forms an amalgam (Damour,
Jour. Prac. Chem., XVII., p. 345). Cobalt is not precipitated
from its neutral solutions by means of zinc, except in the pre-
sence of a metal easily reducible by zinc, e.g., lead or copper,
but not cadmium ; with copper salt present, if the liquid is
acid, copper alone is deposited. A definite quantity cf copper
salt is necessary (Lecoq de Boisbaudran, Jour. Chem. Soc., 1876,
Part II., p. 551). Cobalt is deposited upon steel or iron by
contact of zinc in a boiling hot solution of zinc chloride con-
taining a salt of cobalt (Chem. News, Vol. XXXV., p. 166),
M-ene deposits cobalt upon lead, iron, brass, or copper by
immersing it in contact with zinc in a boiling hot and neutral
( 90 )
solution of chloride of zinc containing fragments of cobalt
(Chem. News, Vol. XXV., p. 214).
Formation of Peroxide of Cobalt. An aqueous solution
of cream of tartar and hydrated cobalt oxide, with a little
soda dissolved in it, yields, with a separate current, a peroxide
of cobalt, exhibiting magnificent colours upon the anode (W.
Wernicke, Watts's "Dictionary of Chemistry," Vol. VII.,
p. 899).
By passing a separate current through a solution of oxide of
cobalt in aqueous potassic cyanide, hydrogen and a small
quantity of cobalt are deposited.
According to Troost and Hautefeuille, laminae of electro-
deposited cobalt sometimes contain as much as thirty- five
times their volume of hydrogen (Chem. News, Vol. XXXI.,
p. 196).
Electrolysis of Fluoride of Cobalt. Co.F 2 . Molecular
weight = 97. I electrolysed a solution of this salt in pure
dilute hydrofluoric acid, by means of a current from a single
Smee cell, with an anode of cobalt and a cathode of copper,
but only a film of black powder appeared on the cathode in
twelve hours.
Electrolysis of Chloride of Cobalt. Co. C1 2 . Molecular
weight = 130. Magnesium decomposes a solution of cobalt
chloride, with evolution of hydrogen and separation of a green
salt containing cobalt oxide (S. Kern, Jour. Chem. Soc., 1876,
Part I., p. 880). Copper immersed in a solution of the double
chloride of cobalt and sodium acquires a coating of cobalt
(Becquerel, The Chemist, Vol. V., p. 408).
In a solution composed of 20 parts of sal ammoniac, 40 of
chloride of cobalt, 20 of aqueous ammonia, and 100 of water,
a brilliant deposit of metallic cobalt was produced upon a
cathode of brass or copper, by means of a current from two
Bunsen cells (M. K. Boettger, Chem. News, Vol. XXXV., p. 16G,
also Jour. Chem. Soc., 1877, Part II., p. 375. To deposit the
met a 1 , dissolve five ounces of its dry chloride in a gallon of
distilled water, and make the solution slightly alkaline by
means of aqueous ammonia. Pass a current from three to
five Smee cells through the solution by means of an anode of
cobalt (Telegraphic Journal, Vol. II., p. 246). By means of a
separate current, an anode of cobalt, and a concentrated solu-
tion of the chloride, with its excess of acid neutralised by
caustic ammonia, Becquerel obtained deposits of the metal,
brilliant, white, hard, and brittle, and possessing magnetic
polarity. He observed that part of the chloride of the solu-
tion was set free during the electrolysis, and that if the liquid
contained iron the greater portion of it was not deposited with
the cobalt (Chem. News, Vol. VL, p. 126).
(91 )
Electrolysis of Sulphate of Cobalt. Co.S0 4 . Molecular
weight = 155. Magnesium slowly deposits hydrated oxide of
cobalt from a solution of the sulphate (Commaille, C/iem. News,
Vol. XIV, p. 188).
By means of a separate current, cobalt is completely precipi-
tated in the metallic state from an aqueous solution of double
sulphate of cobalt and ammonium, if free ammonia is present
(H. Fresenius and F. Bergmann, Chem. News,Vo\. XLIL, p. 75).
Gaifle deposited hard tenacious cobalt of good colour from an
aqueous solution of the double sulphate of cobalt and am-
monium by means of a separate current (Chem. News, VoL
XL., p. 23).
Electrolytic Analysis of Compounds of Cobalt. See
Chem. News, Vol. XLL, p. 25 ; Vol. XLIL, p. 75 ; Vol. XL VI.,
p. 105 ; Jour. Chem. Soc., 1877, Part L. p. 341 ; 1877, Part II.,
p. 925 ; Vol. XXXVL, 1879, p. 588 ; Vol. XXXVIII., pp. 284,
583, and 771 ; Vol. XL., 1881, p. 1,081 ; Vol. XLIL, 1882,
pp. 896, 1,320.
Separation of Iron. Fe. Electro-chemical equivalent
K />
= 28. A dyad cation. From slightly acidified solutions of
ferrous and ferric salts, magnesium deposits iron and hydrogen
gas (Roussin, Chem. News, Vol. XIV., p. 27). Iron in contact
with gold, in acid or neutral, cold or hot solutions of salts of
iron, produces no metallic deposit (Eaoult, Jour. Chem. Soc.,
Vol. XL, p. 646). Metallic iron reduces ferric to ferrous salts
at ordinary temperatures, whilst platinum has no such effect.
Nevertheless, if these two metals are connected together, they
reduce the ferric salt more rapidly than iron alone does, and
the reduced salt forms upon the platinum also, as may be seen
by mixing a little ferricyanide of potassium with- the liquid
(Gladstone and ^Tribe, Phil. Mag. [4], Vol. XLIX., p. 425).
By electrolysis with a separate current iron is incompletely
deposited as metal from neutral solutions of ferrous salts, some
ferric salt being formed. If to the neutral solution of ferrous
sulphate some ammonium citrate be added containing free
citric acid, and care be taken that free citric acid remains in
the solution, the iron will be deposited in the metallic lustrous
form. No iron is separated by electrolysis from a solution of
ferrocyanide of potassium, but prussian blue appears at the
cathode. From the solutions of ferrous oxide in solution of
sodium thio-sulphate, all the iron is separated, chiefly as ferrous
sulphide. From the fluoride of iron dissolved in a solution of
sodium fluoride, metallic iron is deposited (C. Luckow, Jour.
Chem. Soc., Vol. XXXVIII., 1880, p. 284).
' Electrolysis of Ferrous Chloride. Fe.CJ 2 . Molecular
weight = 127. According to Aikin, iron amalgam is
formed by the action of zinc amalgam on ferrous chloride ;
but according to Damour it cannot be produced in this way
(WatU's. "Dictionary of Chemistry," Vol. IIT., p. 888). When
zinc amalgam is immersed in a solution of ferrous chloride,
and a crystal of a nitrate is placed upon it, a black spot is
gradually foimed upon the surface of the amalgam, consisting
of reduced iron, which is immediately taken up by the
m rcury. Chlorates and. other salts do not produce it
(Runge, Watts's "Dictionary of Chemistry," Vol. III., p. 891).
The aqueous solution of ferrous chloride yields by electro-
lysis chlorine and oxygen at the anode, and iron and hydrogen
ait the cathode (Watts's " Dictionary of Chemistry," Vol. Ill,
p. 377).
Electrolysis of Ferric Chloride. Fe 2 Cl c . Molecular
weight = 325. Ferric chloride is partly reduced to ferrous
chloride, partly to metallic iron, by contact with sodium amal-
gam and a little water ; and by contact with a sufficient quan-
tity of the amalgam it is reduced to metal, which remains as
iron amalgam (Cailletet, Watts's " Dictionary of Chemistry,"
Vol. VI., p. 816).
With magnesium and platinum in contact with each other
in a solution of ferric chloride, metallic iron is soon deposited
on the p'atinum. The passage of a feeble current, by means
of platinum, electrodes through a similar solution, sets free
chlorine at the anode and ferrous chloride at the cathode, but
a stronger one deposits metallic iron upon the cathode (Glad-
stone and Tribe, Phil. Mag., 4th Scries, Vol. XLIX., p. 425).
E. Becquerel found that when sesquichloride of iron,
Fe 2 Cl 3 , was electrolysed, one atom of chlorine and atom of
iron are separated for each atom of hydrogen in the voltameter
(Watts's " Dictionary of Chemistry," Vol. IF., p. 439). A con-
centrated acid solution of ferric chloride yields by electrolysis
chlorine and a small quantity of oxygen at the anode, and
ferrous chloride at the cathode (Watt's "Dictionary of Che-
mistry, Vol. Ill, p. 378).
I have deposited metallic iron in a reguline state by passing
a current from 15 or 20 Smee cells through a solution of sal
ammoniac, by means of an anode of sheet iron and a cathode
of copper, for some time, until sufficient iron had dissolved.
M. Cailletet states that by electrolysing a solution of ferrous
chloride mixed with sal ammoniac the iron was deposited in
the form of mammillary masse?, brittle, brilliant, and hard
enough to scratch glass, and the deposit, when plunged into
water, evolved numerous bubbles of pure hydrogen. Also
that one volume of the iron absorbed about 240 volumes of
hydrogen, which ignited by contact with a Hame and sur-
rounded the metal with a pale colour (Chem. Neics, Vol. XXXI.,
p. 119 ; also Jour, Chem. Soc., Vol. XIIL, p. 425). According
( 03)
to K. Leng, deposited iron contains 185 times its volume of
h) 7 drogen, chiefly in the layers of metal first deposited (Chem.
News, Vol. XXL, p. 179), and Troost and Hautefeuille say
that it sometimes contains as much as 260 times its bulk
(Chem. News, Vol. XXXL, p. 196).
Electrolysis of Ferrous Sulphate. Fe.S0 4 . Molecular
weight =152. Sodium amalgam decomposes a solution of
ferrous sulphate, and produces an amalgam of iron (Bottger,
Watts's "Dictionary of Chemistry," Vol. III., p. 887). A
similar amalgam is formed by electrolysing the same solution
with a cathode of mercury (Joule, ibid., p. 888). Magnesium
deposits from a neutral solution of ferrous sulphate hydrated
ferrous oxide ; but from an acidified one it deposits metallic
iron (Commaille, Chem. News, Vol. XIV., p. 188). According
to Fischer, zinc immersed in a perfectly neutral solution of
ferrous sulphate, contained in a stoppered bottle, throws down
metallic iron, partly on the zinc. I have found with this solu-
tion that neither antimony, bismuth, tin, lead, iron, nickel,
copper, brass, German silver, silver, gold, or platinum received
a metallic deposit by simple immersion.
I have deposited firm reguline iron, by means of a separate-
current, from a saturated aqueous solution of a mixture of
two parts of ferrous sulphate and one of sal ammoniac.
Walenn deposited reguline, white, silvery-looking iron, to-
gether with much hydrogen gas, from a cold and slightly acid
solution composed of one part of crystallised ferrous sulphate
and five of water, by means of a current from three Sme&
elements of very large surface. The addition of sulphate of
ammonium increased the conducting power, and formed a very
good conducting liquid (Chem. News, Vol. XVII, p. 170).
Klein employed a solution of ferrous sulphate as pure, neutral,,
and cencentrated as possible ; also a feeble electric current.
These conditions are important. The iron then obtained was
as hard as tempered steel, and very brittle ; but after anneal-
ing it was malleable, and might be engraved as easily as soft
steel. It had a specific gravity of 8'139, and contained
occluded in it 13 times its volume of hydrogen. It possessed
a higher electric conductivity than any commercial iron. It
did not warp when heated, but slightly expanded, and was not
porous (Chem. News, Vol. XVIII., p. 133, and XXL, p. 137;:
also Telegraphic Journal, Vol. II., p. 128).
All ordinary depositing solutions of ferrous salts should be-
protected as much as possible from contact with the atmo-
sphere, because they oxidise ; and a portion of the current
subsequently passed through them is expended in deoxidising;
them. The oxidation is retarded by admixture of glycerine,,
which diminishes their diffusive power. When iron is de-
posited from some of these solutions, and has attained a certain
( 04 )
thickness, brilliant scales of the metal become detached and
fall to the bottom of the liquid.
Electrolysis of Ferrate of Potassium. I have deposited
iron from an aqueous solution of this salt, formed either by
igniting peroxide of iron very strongly for some minutes with
caustic potash and saltpetre, and dissolving the product in
water, or by making a very strong solution of caustic potash,
immersing in it a large iron or steel anode, and a small copper
or platinum cathode, and passing a strong current from 15 or
20 Smee cells through it until it acquires a deep amethystine
or purple colour. By that time the cathode had obtained a
coating of iron, which was in the state of a dark powder if
the powder was too great, but had the appearance of white
cast iron (or intermediate between that and the appearance of
reguline deposited zinc) when the powder was sufficiently weak.
The solution rapidly decomposes, becomes colourless, and
deposits all its metal in the state of peroxide at the bottom of
the vessel.
Electrolysis of Ferrocyanide of Iron. M. II Bojttinger
dissolves 10 parts of ferrocyanide of potassium and '20 of
sodio-potassic tartrate in 200 of water ; then adds a solution
of three parts of ferric sulphate previously dissolved in 50
parts of water, and then, with constant stirring, adds drop by
drop a solution of caustic soda, until the^ precipitate of
Prussian blue is just all redissolved. The resulting solution
may be used for depositing iron upon copper (Cliem. News.
Vol. XXXVI, p. 11).
I have observed that an anode of iron greatly resists the
passage of a current into a solution of perfectly pure potassic
cyanide ; and that if a current of sufficient electromotive force
is employed gas is freely evolved from the iron, and a minute
portion of the metal is dissolved. I have also noticed that if
a very thin wire of silver or gold and one of bright iron be
weighed, then the two twisted together and immersed in a
solution of potassic cyanide contained in a closed bottle, and
set aside for several months, the silver or gold wire has partly
or entirely dissolved, whilst the iron has lost not any or
scarcely any of its weight.
(For the electrolytic analysis of compounds of iron, see
Chem. News, Vol. XXXVIII., p. 26 ; Vol. XLIL, p. 331 ; Vol.
XLVL, p. 105; and Jour. Chem. Soc., 1877, Part I, p. 341 ;
Vol. XXXVIII, 1880, p. 284 ; Vol. XL, 1881, p. 1,081 ; Vol.
XLIL, 1882, pp. 896 and 1,320.)
Separation of Manganese. Mn. Atomic weight = 55-0.
A cation. By the simple immersion of sodium amalgam in an
acidulated solution of a salt of manganese, metallic manganese
is deposited and alloys with the mercury (Roussin, Chem. News,
Vol. XIV., p. 27; Watts's "Dictionary of Chemistry, Vol.
VI., p. 802). According to Phipson, magnesium deposits man-
ganese upon itself by simple immersion in a neutral solution
of a manganous salt (Proc. Eoyal Society, 18G4, Vol. XIIL,
p. 216 ; Chem. News, Vol. IX., p. 219).
Manganese is not deposited in the metallic state by a sepa-
rate current from its neutral or acid solutions, but as hydrated
manganese peroxide. In very dilute solutions of this metal
containing much nitric, or a mixture of nitric and sulphuric
acids, permanganic acid is formed, and colours the liquid (C.
Luckow, Jour. Chem. Soc., Vol. XXXVIIL, p. 284).
Formation of Peroxide of Manganese. The electrolysis,
by a separate current, of a solution of nitrate or acetate of
manganese yields a peroxide at the anode (W. Wernicke,
Watts's " Dictionary of Chemistry," Vol. VII., p. 899 ; Jour.
Chem. Soc., Vol. IX., p. 307). Solutions of salts of manganese
yield peroxide at the anode ; one composed of one part of
manganese chloride dissolved in eight of water yields, with a
platinum wire cathode, very beautiful alternate rings of purple
green, golden yellow, and blue, surrounded by a broad belt
of golden yellow. With a solution composed of one part of
acetate of manganese and fifteen of water, one uniform tint is
invariably produced, first golden yellow, then purple, then
green (B. Bottger, Pogg. Ann., Vol. L., p. 45).
Electrolysis of Manganous Fluoride. Mn.F 2 . Molecular
weight = 93*0. I melted some fluoride of manganese in a pla-
tinum crucible, and employed two spirals of platinum wire as
electrodes, and a current from six large Smee cells. The con-
duction was moderate, and gas was evolved from the anode.
In a few minutes both the cathode and the crucible became
quite rotten by the union of the deposited manganese with the
platinum. The anode was not corroded. I also melted the
same salt in a crucible of copper, and passed the current by
means of a sheet platinum anode and sheet copper cathode during
half an hour. The conduction was free, abundance of gas was
evolved from the anode, but none from the cathode, and it
ceased on stopping the current. The deposit on the cathode
was black, and did not evolve hydrogen with dilute hydro-
chloric acid, and was therefore not metallic manganese. The
crucible was much corroded at the line of surface of the
liquid.
I also electrolysed a dilute solution of fluoride of manganese
by a current from six Grove cells and electrodes of platinum.
Much heat was evolved, gas was set free at the anode, and a
film of black deposit formed upon the cathode. By similar
treatment of a saturated solution of the salt, not containing
any free hydrofluoric acid, a film of purple colour was instantly
formed upon the anode, but it dissolved quickly, and did not
( 93)
colour the liquid. Gas came from both electrodes freely ; the
liquid also became heated. No solid deposit was obtained.
Electrolysis of Manganous Chloride. Mn.Cl 2 . Mole-
cular weight = 126. By the simple immersion of an amalgam
of sodium in a saturated aqueous solution of this salt, Giles
deposited manganese upon the surface of the amalgam (Phil.
Mag., 4th Series, Vol. XXIV., p. 328). It produces a viscid
amalgam of manganese and mercury. According to S. Kern,
magnesium deposits only manganous oxide (Jour. Chem. Soc. 9
1876, Part 2, p. 479).
Bunsen filled a porous cell with a hot, saturated, aqueous
solution of this salt, placed it in a charcoal crucible containing
hydrochloric acid to the same level, kept the whole arrange-
ment hot, and passed a current from four Bunsen cells from
the crucible to a platinum wire immersed in the manganous
solution. Metallic manganese was easily and freely deposited ;.
but if the density of the current at the cathode was reduced
by any means, or the concentration of the solution diminished,
black manganous manganic oxide alone was obtained (The
Chemist, No. XL, August, 1854, p. 685; Watts's "Dictionary
of Chemistry," Vol. II., p. 438).
Electrolysis of Manganous Sulphate. Mn.S0 4 . Mag-
nesium deposited hydrated manganous oxide from a neutral
solution of this salt, but from the same solution acidified it
deposits metallic manganese (Commaille, Chem. News, Vol.
XIV., p. 188).
(For the electrolytic analysis of compounds of manganese,
see Jour. Chem. Soc. t 1877, Part 2, p. 924, Vol. XXXVIIL,
p. 284, Vol. XLIL, 1882, pp. 896, 1320; Chem. Ntwt, Vol.
XL VI., p. 105.)
Deposition of Chromium. Cr. Atomic weight = 52-5. A
cation. A slightly acidified solution of chromic chloride or
other chromic salt yields with sodium amalgam an easily de-
composable liquid alloy, which, when heated in a stream of
hydrogen or vapour of naphtha, loses its mercury and leaves
metallic chromium in a spongy state. The liquid turns green
previous to reduction (Bunge, Watts's "Dictionary of
Chemistry," Vol. VI., p. 816 ; Roussin, ibid, Vol. VI., p. 449 ;
Vincent, Phil. Mag., 4th Series, Vol. XXIV., p. 328). Mag-
nesium precipitates only the hydrated sesquioxide of chromium
from a solution of chromous and chromic chloride (Commaille,
Chem. News, Vol. XIV., p. 188). _
By means of a current from six Grove cells with platinum
electrodes, I electrolysed a strong solution of fluoride 06
chromium containing some free hydrofluoric acid and a little-
hydrochloric acid. The liquid soon became hot ; no gas was
liberated at the cathode, but chlorine and ozone were set free
at the anode, whi-jh was not corroded. I also passed a current
(97)
from five Smee elements, by means of electrodes of platinum,
through some acid potassic chromate in a state of fusion. A
deposit slowly formed upon the cathode.
By operating in a similar manner upon a concentrated solu-
tion of chloride of chromium as upon one of manganese,
Bunsen deposited chromium readily. The deposit appeared
like iron, but was less affected by damp air. It resisted the
action of boiling nitric acid, but was soluble in hydrochloric or
dilute sulphuric acid. It was friable, and presented a polished
surface on the side next the cathode. On diminishing the
density of the current a black powder was deposited, contain-
ing more oxygen in proportion as the current was decreased.
Adding protochloride of chromium had the opposite effect ; i.e.,
it caused metallic chromium to be deposited (The Chemist,
No. 11, Aug. 1854, p. 686 ; Watts's "Dictionary of Chemistry,"
Vol. II, p. 438).
(For the electrolytic analysis of compounds of chromium see
Jour. Chem. Soc. t Vol. XLIL, p. 896.)
Deposition of Uranium. Ur. Atomic weight = 120 A
cation. Magnesium deposits gold-coloured hydrated sesqui-
oxide of this metal by simple immersion in an aqueous solu-
tion of the oxalate of uranium (Commaille, Chem. News, Vol.
XIV., p. 188). Magnesium decomposes an aqueous solution
of uranic nitrate with evolution of hydrogen, and produces
uranic oxide (S. Kern, Jour. Chem. Soc., 1876, Part 2, p. 479).
I melted some fluoride of uranium in a platinum crucible, and
added to the liquid some crystals of silicon ; the salt was not
decomposed.
Solutions of uranium in mineral acids are not precipitated by
.a current from two to four Meidinger-Pmcus elements, but the
nascent hydrogen reduces the uranic to uranous oxide. From
neutral solutions it is separated in very small quantities of a
yellow colour. Alkaline solutions containing acetic, citric, or
tartaric acid or sugar also deposit by electrolysis small quan-
tities of uranium. The deposited uranium does not readilydis-
solve in dilute acids (Schicht, Chem. News, Vol. XLL, p. 280).
I passed a current from six Grove cells, by means of plati-
num electrodes, through an aqueous solution of fluoride of
uranium. Much gas, having the odour of ozone, was evolved
at the anode, and the liquid became hot. On adding some
-aqueous hydrofluoric acid the conduction became very free,
.and more gas was liberated from both electrodes, but no solid
deposit was formed.
I also fused some fluoride of uranium in a copper crucible,
and passed a current from six Smee cells through it by means
of a platinum wire anode, using the crucible as a cathode ; a
little gas was set free at the anode, and the crucible melted.
A second trial was made, using a platinum crucible, and two
(98)
spirals of platinum wire as electrodes, and the current
continued during one hour. Conduction was very free,
much gas was evolved from the anode, but none from
the cathode; a bulky deposit quickly formed upon the
negative spiral, especially on the side towards the anode. The
deposit weighed 43-66 grains, and consisted of hard jet black
crystals. The anode was not corroded. In a third trial four
Grove cells were employed, and a special apparatus devised
and employed to collect the evolved gas ; about five cubic
inches were obtained. The crystals were not metallic uranium ;
they were insoluble in boiling water, but soluble in cold dilute
hydrofluoric acid, without evolving gas. About one-fourth of
the deposit consisted of a fine crystalline powder, nearly of
the colour of copper, but darker, and was composed of the
crystals, with a film of less reduced fluoride upon them ; they
evolved gas in cold nitric acid, or in hot dilute nitric acid.
They were not fused by heating alone to redness upon plati-
num foil, but if caustic potash was added they oxidised. I also-
electrolysed a fused mixture of the pure fluorides of uranium
and potassium with platinum electrodes. The results were very
similar, except that the deposit upon the cathode fell off as
fast as it was formed, and the crystals had to be extracted by
dissolving the cooled saline mass in slightly diluted and hot
hydrochloric acid. They were very much like those of silicon ;
their form was that of a short pyramid with a square base. The
anode was very slightly corroded, and made bright by the
action, and twenty cubic inches of gas were collected from it.
By electrolysis with a separate current uranium is obtained
in small quantity only, even from the completely neutral solu-
tion of the oxide, as a yellowish grey metallic precipitate,
soluble in hydrochloric acid (C. Luckow, Jour. Chem. Soc. t Vol.
XXXVIIL, 1880, p. 284).
On passing the current from two elements of a bichromate
of potassium battery through an aqueous solution of uranium
acetate, formiate or nitrate, bright yellow uranium oxide,
Ur 3 4 , was separated at the cathode, and gradually became
black. No uranium remained in the solution after the current
had been passed two hours. The black compound was uranic
uranous oxide, containing 81-13 per cent, of uranium (E. F.
Smith, Chem. News, Vol. XLIIL, p. 61, also Jour. Chem. Soc. y
Vol. XXXVIIL, p. 284, Vol. XL., 1881, p. 3). According to
the same author, molybdenum, tungsten, vanadium, didymium,
and cerium are not completely precipitated from their solu-
tions by the voltaic current.
(For the electrolytic analysis of compounds of uranium see
Chem. News, Vol. XLIL, p. 331.;
Separation of Tungsten. W. Atomic weight = 184.
A cation. When tungsten trioxide solutions are reduced by
( 99)
zinc, the final product of the action is tungsten dioxide (0.
Freih, Jour. Chem. Soc., 1883, Vol. XLIV., p. 785). I fused
some sodic tungstate to a clear liquid in a porcelain vessel,
and electrolysed it by means of a current from five Smee
elements, a gas carbon anode, and a platinum wire cathode.
The conduction was moderately free, gas was evolved from the
anode, and at the cathode black matter was set free, floated,
diffused in the liquid, and became partly redissolved, Accord-
ing to E. F. Smith, neutral solutions of the tungstates are not
affected by the current (Chem. News, Vol. XLIIL, p. 61).
Separation of Vanadium. Va. Atomic weight = 137.
L. Schicht dissolved vanadium chloride in water containing
hydrochloric acid, and electrolysed the solution. No depo-
sition took place in the blue liquid, the vanadic acid being
merely reduced to oxide (Chem. News, Vol. XLL, p. 280, and
XLIL, p. 331). I electrolysed a solution composed of vanadic
acid dissolved in pure dilute hydrofluoric acid, by means of
a current from 10 Smee elements, with a gas carbon anode
and platinum cathode. Gas, having an odour of ozone, was set
free at the anode. I also saturated dilute sulphuric acid with
pure vanadate of ammonia, and electrolysed the solution with
platinum electrodes, and a current from four zinc and platinum
elements excited by dilute sulphuric acid. Conduction was
very sparing ; the solution slowly became of a very intense
bluish black colour at the cathode, and a jet black powder of
some thickness was deposited upon it.
(For the electrolytic analysis of vanadium compounds see
Jour. Chem. Soc., Vol. XLIL, 1882, p. 896.)
Separation of Molybdenum. Mo. Atomic weight =
96. A cation. Sodium molybdate is not reduced by metallic
tin (Ullik, Watts's "Dictionary of Chemistry," Vol. VI., p.
832). From an ammoniacal solution of molybdic anhydride,
by means of a separate current, molybdenum is completely
and firmly deposited upon the cathode as molybdous oxide in
coloured rings which thicken and become black. The first blue
precipitate is molybdic molybdate, then follow molybdic and
molybdous oxides. In acid solutions there is no deposit. In
ammonium molybdate acidified with molybdic anhydride the
precipitation is incomplete (L. Schicht, Jour. Chem. Soc., Vol.
XXXVIIL, 1880, p. 747; Chem. News, Vol. XLL, p. 280, and
Vol. XLIL, p. 331).
Molybdic acid dissolves freely in pure dilute hydrofluoric
acid, evolving a little heat. I electrolysed the solution both
with a platinum and with a gas carbon anode and a current
from ten large Smee cells. The colourless liquid conducted
freely, becoming instantly of an indigo blue colour at a pla-
tinum cathode. Gas was set free at each electrode ; that from
the carbon anode was the most abundant, and had a slightly
H 2
(100)
chlorous odour. On stopping the current the deep blue film
on the cathode quickly dissolved, and the liquid soon became
colourless. During the action the cathode was several times
removed and dipped into water ; much blue matter dissolved,
but the water became nearly colourless in half a minute, even
without stirring, and however large the quantity of the blue
matter was which dissolved it.
I also fused some molybdic acid in a porcelain crucible, and
passed a current through it from five Smee elements, by means
of a gas carbon anode and platinum cathode. It conducted
freely. The action was rather strong at the anode, but little
gas was set free. No gas was evolved at the cathode, but
crystals quickly collected upon it in a large mass, which soon
filled the entire solution and spread to the anode. The carbon
was not disintegrated or dissolved. The cooled residue was a
black mass of crystals. In a second trial with a current from
12 similar cells, and a platinum anode and cathode, much gas
was set free at the cathode, and less from the anode, and the
bluish black deposit formed upon the cathode. A large number
of crystalline needles, from th to th of an inch long, stood
out at right angles upon the surface of the cathode in the liquid.
The deposit imparted a transient green colour to water.
Crystals of dioxide of molybdenum, Mo0 2 , quickly become
.covered with copper when immersed in a solution of cupric
sulphate in contact with zinc (Ullik, Watts's "Dictionary of
Chemistry," Vol. VI., p. 832).^
(For the electrolytic analysis of molybdenum compounds see
E. F. Smith, Chem. News, Vol. XLIIL, p. 6; and also Jour.
Chem. Soc., Vol. XL., 1881, p. 3.)
Separation of Lead. Pb. Electro-chemical equivalent
_ . = 103-5. A dyad cation. The deposition of lead by the
simple immersion of zinc in a solution of nitrate or acetate of
lead is a very old fact, and when the zinc is in the form of a
spiral wire it constitutes the well-known " lead tree." Accord-
ing to A. Cossa an alkaline solution of plumbic chromate is at
once decomposed by aluminium, with deposition of lead and
formation of chromic oxide (Watts's "Dictionary of Chemis-
try," Vol. VII., p. 54). Thallium deposits lead from a solu-
tion of plumbic acetate (W. C. Keid, Chem. News, Vol. XII.,
p. 242). Lead in contact with gold in acid or neutral, cold or
hot, solutions of salts of lead, produces no deposit of lead
(Raoult, Jour. Chem. Soc., Vol. XL, p. 646).
Electrolysis of Plumbic Nitrate. Pb2N0 3 . Molecular
weight = 331. A solution of this salt is slowly decomposed by
contact with aluminium, and the lead deposited in crystals
{A. Cossa, Watts's "Dictionary of Chemistry," Vol. VII.,
p. 54). Magnesium immersed in a solution of plumbic nitrate
is quickly covered with lead powder, which quickly oxidises.
(S. Kern, Jwr. Chem. Soc., 1876, Part L, p. 683). In a solu-
tion of hyponi trite, nitrate, or acetate of lead, zinc received a
coating of lead by simple immersion, but antimony, bismuth,
tin, lead, iron, nickel, copper, brass, German silver, silver,
gold, or platinum did not. A solution of the nitrate yields by
electrolysis with a separate current peroxide of lead at the
anode.
Electrolysis of Plumbic Fluoride. PbF 2 . I fused some
of this salt in a platinum crucible, and added some crystals of
boron ; vivid incandescence occurred, and melted lead was
separated. The addition of crystals of silicon had a similar
effect. Metallic antimony or copper did not liberate lead. By
stirring the melted salt with an iron rod heat was evolved, the
iron corroded, and lead was set free. The addition of zinc to
the fused salt caused an explosion, and magnesium produced
quite a dangerous detonation.
Beetz electrolysed this salt in a fused state by a separate
current, and observed that a colourless gas was evolved from
the anode, and lead set free at the cathode (The Chemist,
New Series, Vol. I., p. 253). G. J. Knox electrolysed it with
an anode of charcoal and a cathode of platinum wire by means
of a current from sixty voltaic cells (Phil. Mag., 3rd Series,
Vol. XVL, p. 192). Fremy found it easily decomposed by a
separate current; lead was deposited (The Chemist, New Series,
Vol. II., p. 548). I melted 400 grains of the pure salt in a
thick copper crucible, and electrolysed the liquid by means of
a current from six Smee cells, using a platinum wire anode
and a copper wire cathode. Conduction was copious ; a bulky
crust quickly formed upon the cathode, and advanced towards
the anode in lumpy projections. A little gas appeared at the
latter, but during a short time only. The deposit upon the
cathode was not lead, nor was there any metal contained in a
free state in it, nor in the saline mass, after action lasting one
hour ; it was a mass of lead salt, brittle and of a red-brown
colour (like that of peroxide of lead) when cold. The conduc-
tion was very perfect, and the fused salt appeared to conduct
without being decomposed. The anode was not corroded. I
also electrolysed the fused salt in a deep, narrow, and thick
copper cup, with an anode of gas carbon, during one and
a-quarter hour. The anode was corroded, and the metal
liberated ; action was copious, gas was evolved at the anode,
and about seven or eight cubic inches were collected.
Electrolysis of Plumbic Chloride. Pb.Cl 2 . Molecular-
weight =278. According to Commaille, magnesium deposits
lead, together with much hydrogen, from a neutral solution of
this salt (Chem. News, Vol. XIV., p. 188). Aluminium imme-
diately deposits crystals of lead from it (A. Cossa, Watts'a
( 102 )
" Dictionary of Chemistry," Vol. VII, p. 54). According to
Becquerel, if a piece of bright copper in contact with zinc be
immersed in a solution of the chlorides of lead and sodium it
becomes coated with lead (The Chemist, Vol. V., p. 408).
Faraday found that the proportion of lead deposited from
its fused chloride to that of water decomposed by the same
current was as 100-85 to 18 (Watts's "Dictionary of Chemistry,"
Vol. II., p. 439). According to Buff, solid lead chloride con-
ducts like a metal i.e., without decomposition but rise of
temperature increases its conductivity (Jour. Chem. Soc., 1876,
Part I., p. 668). Faraday found that by passing a current
through the melted salt chlorine appeared at the anode and
lead at the cathode.
Electrolysis of Plumbate of Potash. Metallic zinc or tin,
but not iron, becomes coated with lead by simple immersion in
a solution formed by dissolving litharge in a boiling hot solu-
tion of caustic potash.
Haeffelly deposits lead upon copper or brass by immersing
them in contact with a piece of tin in a hot alkaline solution
of oxide of lead. The tin dissolves in the form of an alkaline
stannate, and the lead is deposited in a spongy state (Chem.
Neivs, Vol. VI., p. 163). I connected together a wire of zinc
and one of platinum, and immersed the pair in a solution of
litharge in strong aqueous ammonia; both wires became coated
with a black deposit in a few minutes. By contact with air,
the moist deposit became yellow, and was apparently recon-
verted into litharge. F. Weil coats copper, iron, and steel
with lead, by dissolving a salt of lead in a strong solution of
potash or soda, and immersing them in the liquid in contact
with zinc; the deposit, however, contains zinc. To obtain it
pure, the piece of zinc is placed in the alkaline lixivium in a
porous cell, and the cell immersed in the lead solution, the
zinc being connected with the copper, &c., by a wire (Chem.
News, Vol. XIII., p. 2).
Electrolysis of Plumbic Acetate. According to A. Cossa,
aluminium slowly deposits lead in crystals from a solution of
this salt (Watts's " Dictionary of Chemistry," Vol. VII, p. 54).
By a separate current, this solution yields peroxide of lead at
the anode.
Formation of Peroxide of Lead. According to W. Wer-
nicke, an alkaline solution of the tartrate of lead and sodium,
with platinum electrode and a current from two Daniell cells,
yields a black deposit of peroxide of lead upon the anode ; and
a solution of one part of plumbic nitrate and eight of water
gives a similar deposit by such treatment (Jour. Chem. Soc.,
Vol. IX., p. 306 ; Chem. News, Vol. XXII, p. 240).
Nobili, in the year 1826, discovered that if a solution of
acetate of lead be electrolysed by means of a large sheet
( 103 )
platinum anode and a platinum wire cathode, a deposit is
formed upon the positive plate; and that if a polished steel
plate be employed as the anode, with a current from four or
six Grove cells, the deposit is in the form of a thin film, and
exhibits all the colours of the spectrum ; and by placing the
positive plate horizontally beneath the vertical negative wire
the colours are in the form of rings, the centre of which is
the wire, and are arranged in the order of the chromatic scale.
These colours are known as " Nobili's rings." Becquerel, Gas-
siot and others have, by varying the strength of the battery
and of the solutions employed, and interposing non-conducting
patterns between the anode and cathode, and by using cathodes
of different shapes, obtained effects of great delicacy and
beauty. Salts of other metals, such as bismuth, silver, nickel,
cobalt, manganese, &c., which yield deposits of peroxide at the
anodes, may be employed instead of those of lead. Becquerel
prepared his plumbic solution as follows : Dissolve 200
grammes of caustic potash in two quarts of distilled water, add
150 grammes of litharge, boil the mixture half an hour, allow
it to become clear, take the clear portion and dilute it with its
own bulk of water (The Chemist, Vol. IV., p. 457). The solu-
tion is used cold, and is rapidly deprived of its metal, because
lead is deposited upon the cathode at the same time.
By this means may be imparted to polished surfaces of metals
all the richest colours of the rainbow. " They commence with
silver blonde, and progress onwards to fawn colour, and thence
through various shades of violet to the indigo and blues; then
through pale blue to yellow and orange; thence through lake
and bluish lake to green and greenish orange and rose orange;
thence through greenish violet and green to reddish yellow
and rose lake, which is the highest colour on the chromatic
scale" (Walker's "Electrotype Manipulation," Part XL, 16th
edition, p. 40). Too great a strength of the current covers all
the tints with an uniformly dark brown coating. The deposits,
if properly prepared, resist friction well. The process is termed
"Metallo-chromy."
Metallo-chromy effected by means of a solution of oxide of
lead in caustic soda, or potash, is largely employed in Nurem-
burg to ornament metallic toys (Wagner's "Technology,"
p. 117). Bells are similarly coloured in France, and the hands
and dials of watches in Switzerland.
Electrolytic Analysis of Compounds of Lead. See Jour.
Chem. Soc., Vol. XXXVIIL, 1880, p. 284 ; Vol. XLIL, 1882,
p. 1,320 ; Chem. News, Vol. XXXV., p. 264; Vol. XL VI., p. 106;
Watts's " Dictionary of Chemistry," Vol. VIIL, Part I., p. 712,
Part II, p. 1,168.
(For Keith's process for desilvering lead by means of an
electric current, see Jour. Chem. Soc., 1877, Part XL, pp. 804
(104)
and 924; Vol. XXXVI., 1879, pp. 288 and 410; and for
Blagden's process, see Watts's ''Dictionary of Chemistry,"
Vol. VI , p. 1,026 )
Separation of Thallium. Tl. Electro-chemical equiva-
lent = 204. A monad cation. Zinc coats itself with metal in
solutions of salts of thallium, but tin usually does not. Ac-
cording to Lamy, zinc precipitates the metal from the solu-
tions of the nitrate and sulphate in the form of brilliant
crystalline laminae. I found that crystals of silicon had no
reducing effect on a solution of fluoride of thallium containing
free hydrofluoric acid. According to A. Cossa, aluminium
deposits by simple immersion metallic thallium from a solu-
tion of thallium chloride at 90 C. (Watts's " Dictionary of
Chemistry," Vol. VII., p. 54).
Solutions of the salts of this metal are easily decomposed
by a feeble current, and the metal deposited in beautiful cry-
stalline plates upon the cathode. I electrolysed an aqueous
solution of the fluoride by a current from a single Smee
element, a thallium anode and a platinum cathode. It con-
ducted freely, and quickly gave a metallic deposit, in long
feathery crystals, like those of electro-deposited tin, but of a
less white colour.
According to L. Schicht, acidulated solutions of nitrate and
sulphate of thallium were not precipitated by a separate cur-
rent. From ammoniacal solutions thallium was deposited
upon the cathode together with much gas ; whilst at the anode
there appeared blackish brown thallium oxide much re-
sembling peroxide of lead. The current was from four
Meidinger-Pincus elements, and yielded the metal in a spongy
state and of a dark colour ; but by using only two or three
cells, fine permanently adhesive metal was obtained. From
neutral solutions the metal is imperfectly precipitated on
account of the acid which is liberated, but in alkaline ones the
metal is bright and solid, and the deposition is complete. The
deposit redissolves readily in sulphuric acid (C/iem. News, Vol.
XLL, p. 280 ; also Vol. XLVIL, p. 209).
Electrolysis of Sulphate of Thallium. T1 2 S0 4 . Mole-
cular weight = 504. Aluminium immersed in a slightly acid
solution of thallium sulphate becomes coated in ten days with
regular octohedra of thallium alum (Watts's "Dictionary of
Chemistry," Vol. VII., p. 54). A solution of sulphate of
thallium, acidulated with sulphuric acid, deposits its metal
upon zinc by simple immersion (Chem. News, Vol. XXXVI.,
p. 166).
A thallium anode, in water acidulated with sulphuric acid,
is converted into the black trioxide by a current from two
Bunsen cells (Watts's " Dictionary of Chemistry," Vol. VI.,
p. 1,082).
( 105)
The metal is i educed from its solutions, generally from the
sulphate, either by a separate current or by simple immersion
of zinc. When a current from two or three Grove cells, with
platinum electrodes, is passed through an acidulated solution
of thallium sulphate, dissolved in its own weight of water, the
metal is deposited upon the cathode in brilliant plates and
long needle-shaped crystals stretching out towards the anode.
The reduction is complete when hydrogen begins to escape at
the cathode (Crookes, Watts's " Dictionary of Chemistry,"
Vol. V., p. 743).
(For the electrolytic analysis of compounds of thallium, see
L. Schicht, Chem. News, Vol. XLIL, p. 331.)
Separation of Indium. In. Atomic weight = 113 -4. A
cation. This metal being very costly, but little has been done
with it in electro-chemistry. It is deposited from solutions
by simple immersion of zinc in them.
According to L. Schicht, indium is completely deposited as
a bluish white metal at the cathode by a separate current, both
from acid and from alkaline solutions. In the latter case the
metal is very bright and firm. With solutions containing
organic acids, indium is also deposited in a coherent state, with
abundant escape of gas (Chem. News, Vol. XLL, p. 280 ; also
Vol. XLVIL, p. 209).
(For the electrolytic analysis of compounds of indium, see L.
Schicht, Chem. News, Vol. XLIL, p. 331.)
Separation of Tin. Sn. Atomic weight = 118. A cation.
Very few solutions of tin are available for electrolysis; the
chief are stannous chloride and the aqueous solutions of
stannous and stannic fluoride.
M. H. Loewel added metallic tin to a solution of green
crystallised chloride of chromium free from excess of acid, in
a closed glass vessel, and boiled the mixture during about 10
or 12 minutes, and then allowed it to cool. During the heat-
ing the tin combined with the chlorine of some of the chromium
salt, forming stannous chloride and chromous chloride ; but
during the cooling the action was reversed, the chromous
chloride took chlorine from the stannous chloride, and metallic
tin was deposited in the form of numerous small plates (The
Chemist, Part VIIL, May, 1854, p. 476).
Electrolysis of Stannous Fluoride. Sn.F 2 . Molecular
weight =156. I found that zinc, immersed in a solution of
stannous fluoride, produced a flocculent precipitate, and evolved
gas. In the same liquid, but containing free hydro-fluoric
acid, crystals of silicon did not deposit tin by simple immer-
sion. Fremy electrolysed fused fluoride of tin in a platinum
vessel ; it was easily decomposed ; the deposited metal alloyed
( 106 )
with and perforated the vessel in a few minutes (The Chemist,
New Series, Vol. II., p. 548). I electrolysed a saturated non-
acid solution of stannous fluoride by means of large pla-
tinum electrodes, and a current from 10 large Smee cells;
the conduction was sparing, a little oxygen was evolved
at the anode, and long feathery crystals of tin were slowly
formed upon the cathode. No gas appeared at the cathode
or solid deposit at the anode. By using only one Smee cell
the deposit of tin was white, and beautiful crystals of the
metal soon reached across the liquid, and completed the
metallic circuit by touching the anode.
Also by passing a current from six Grove elements by
means of platinum electrodes through a strong aqueous solu-
tion of stannic fluoride containing little or no free hydrofluoric
acid a grey deposit of tin soon appeared on the cathode. The
conduction was free, much gas came from the anode, and heat
was evolved in the liquid. The anode was not corroded, nor
did it acquire any solid deposit.
Electrolysis of Stannous Chloride. Sn.Cl 2 . Molecular
weight =189. Electrolytic experiments for the separation of
tin are usually made with solutions containing this salt.
Magnesium deposits stannic acid and spongy tin from this
solution (Commaille, Chem. News, Vol. XIV., p. 188). A "tin
tree" is produced by immersing a spiral of zinc wire in ten to
twenty ounces of water in which has been dissolved three
drachms of this salt and ten drops of nitric acid, and allowing
the arrangement to remain undisturbed. According to
Bottger, sodium amalgam in contact with a concentrated
solution of stannous chloride forms a viscid amalgam. Joule
obtained a beautiful crystalline amalgam by using a separate
current and making mercury the cathode in this liquid.
I have observed that zinc and lead become tinned by simple
immersion in a solution of the salt, but antimony, bismuth,
platinum, gold, silver, copper, brass, German silver, nickel,
iron, and tin do not. According to Raoult, gold or copper in
contact with tin in a concentrated and boiling solution of
stannous chloride receive a deposit of tin ; but gold in contact
with antimony, silver, copper, nickel, iron, or lead receives
no such coating in either the hot or cold liquid (Chem. News,
Vol. XXVI., p. 240, and XXVII., p. 59; also Jour. Chem.
Soc., Vol. X., p. 464).
Zinc or iron previously coated with a film of metallic copper
by simple immersion process acquire a deposit of tin by simple
contact with a solution composed of one part of crystals of
stannous chloride, two of water, and two of hydrochloric acid
(C. Paul, Jour. Chem. Soc., Vol. XL, p. 955). According to
Roseleur, zinc and iron become tinned by simple immersion in
a boiling hot solution composed of one part of fused stannous
( 107)
chloride, thirty of ammonium alum, and 2,000 of water; zinc
also acquires a coating of tin. by simple contact with a solution
of one part of fused stannous chloride and five of pyrophos-
phate of sodium, dissolved in 300 parts of distilled water.
Copper, brass, and bronze become coated with tin by con-
tact during a few minutes with that metal in a boiling hot
solution of peroxide of tin in caustic potash. F. Weil coats
copper with tin by immersing it, in contact with zinc, in a
solution formed by dissolving a salt of tin in a strong solution
of caustic potash or soda, the liquid being at 50 to 100C.;
the deposit, however, contains zinc (Chem. Neivs, Vol. XIIL,
p. 2). Dr. Hillier tins metals by immersing them in contact
both with tin and zinc in a hot solution of one part of stannous
chloride dissolved in 20 of water, to which has next been
added one or two parts of caustic soda in 20 of water.
According to Becquerel, copper and iron become tinned by
immersion in contact with zinc in a dilute solution of the
double chloride of tin and sodium at 160 F., but are
not tinned by simple immersion alone in that liquid (The
Chemist, Vol. V., p. 408). For coating iron with tin by
immersion in a liquid in contact with zinc Roseleur recom-
mends a solution prepared thus : Take equal weights of
stannous chloride, cream of tartar, and water. Dissolve the
chloride in one-third of the cold water, warm the other por-
tion of water and dissolve the cream of tartar in it. and mix
the solutions ; the mixture is clear, and has an acid reaction.
And a second solution, composed of six parts of crystal, or four
of fused stannous chloride, and 60 of pyrophosphate of
potassium or sodium, dissolved in 2,000 parts of distilled
water. The size of the zinc should be about # that of the
iron. The deposition occupies several hours. When the
solution becomes weak equal weights of the pyrophosphate
and fused chloride are added.
M. Heeren coats iron with tin by immersing it during two
hours, in contact with zinc, in a solution of two parts of
tartaric acid, three of stannous chloride, and three of caustic
soda, and 100 of water (Jour. Chem. Soc., Vol. XIIL, p. 672).
Stolba uses a solution of 5 to 10 parts of stannous chloride
dissolved in 100 of water, and a very minute amount of cream
of tartar added. The metal to be coated is wetted with the
solution whilst in contact with particles of zinc spread over its
surface (Chem. News, Vol. XXIII., p. 21). Brass and copper
acquire a coating of tin if placed in contact with that metal in
a boiling hot saturated solution of cream of tartar.
By means of the single cell process F. Weil coats copper
with tin in a solution of a salt of tin in strong caustic potash
or soda. A porous cell, containing a solution of the potash or
soda, is placed in the bath, a piece of zinc immersed in it, the
copper immersed in the hot tinning liquid, and the two metals
(108)
connected together by a wire. The deposit is pure tin, and
may be obtained of any thickness. To revive the inner liquid,
precipitate the dissolved zinc from it by addition of solution
of sulphide of sodium (Chem. News, Vol. XIII., p. 2).
By means of a separate current, fused stannous chloride
yields tin at the cathode, whilst vapour of stannic chloride
escapes at the anode (Faraday). He found by experiment that
the proportion by weight of tin deposited from fused stannous
chloride, and of water decomposed by the same current was
as 117-16 to 18 (Watts's "Dictionary of Chemistry," Vol. II.,
p. 439). Iron may be quoted with a beautiful white deposit of
tin by making it the cathode in a solution of stannate of potash ;
but the solution is gradually decomposed by contact with the
atmosphere, and deposits peroxide of tin.
Various solutions yield tin by this method. Eoseleur's is
composed of six parts of crystals of stannous chloride, and
50 of pyrophosphate of sodium, dissolved in 5,000 parts of dis-
tilled water, the two salts being dissolved in separate portions
of the water, and the solutions mixed, and then stirred till
clear. It requires a largo anode and a strong current. (For
various other electrolytic mixtures containing stannous chloride
and other ingredients, see " The Art of Electro-Metallurgy,'*
Longman's "Text-Books of Science," pp. 270-272.)
Anhydrous stannic chloride did not conduct a current from
8,040 cells of W. de la Rue's chloride of silver battery (Bleek-
rode, Proc. Roy. Soc. t Vol. XXV., p. 325).
Separation of Alloys of Copper and Tin. Iron is said to
acquire a deposit of bronze by simple immersion in a solution
of 4 to 5 parts of cupric sulphate, 4 to 5 of crystallised
stannous chloride, and 100 of water.
For depositing bronze by a separate current, Salzede used a
solution composed of cupric chloride, stannous chloride, nitrate
of ammonium, and potassic carbonate and cyanide, dissolved
in water. For the same purpose Newton used one composed
of the tartrates of copper, tin, and potassium.
Formation of Crystals of Tin by Electrolysis. The
crystallisation of tin is a phenomenon conspicuously striking
under some conditions in a solution of stannous chloride. The
crystals of tin formed upon the cathode increase so rapidly in
length as to grow across the solution, and touch the positive
pole in a few minutes. And if the solution and current are
strong and the cathode small, quite a mass of crystals will
soon fill the liquid and converge towards the anode. If the
anode be drawn farther away in the solution the crystals follow
it. The largest crystals are produced by slow action; to pro-
duce them a platinum capsule is covered with an outer coating
of wax, leaving the bottom uncovered, and then set upon a
plate of amalgamated zinc in a porcelain vessel. The capsule is
(109)
then filled completely with a dilute and not too acid solution
of stannous chloride, whilst the outer vessel is filled with water
(containing one-twentieth its bulk of hydrochloric acid) up to
such a height that the two liquids come into mutual contact.
The electric current generated reduces the salt of tin, and in a
few days the crystals upon the interior of the capsule are well
developed, and should be washed with water and dried quickly
<F. Stolba, Chem. Neivs, Vol. XXX., p. 177).
For the electrolytic analysis of compounds of tin see Chem.
News, Vol. XL VI., p. 106. Also Watts's " Dictionary of
Chemistry," Vol. VI., p. 676; Jour. Chem. Soc., Vol. XL.,
1881, p. 1,081, Vol. XLIL, 1882, p. 1,320.
Separation of Cadmium. Cd. Electro-chemical equivalent
= - = 56. A dyad cation. Sodium amalgam decomposes a
a
solution of a salt of cadmium, and forms cadmium amalgam
(Bottger). From a solution of the chloride, magnesium
deposits, with strong action, a mixture of cadmium and an
oxy-chloride of the same metal (Commaille, Chem. News, Vol.
XI V., p. 188). I have found that crystals of silicon heated
with cadmic fluoride set free cadmium.
According to Kaoult, gold or copper in contact with cad-
mium in a concentrated and boiling solution of cadmium sul-
phate or chloride decomposes these salts, and quickly deposits
a white, brilliant, and firmly adherent but thin film of cad-
mium upon the gold or copper, even when the solution is not
acidulated and no hydrogen evolved. The experiment does
not succeed with the nitrate. But gold in contact with iron,
nickel, antimony, lead, copper, or silver, in cold or boiling acid
or neutral solutions of salts of cadmium, receives no such de-
posit (Chem. News, Vol. XXVI., p. 240 ; Vol. XXVII., p. 59 ;
Jour. Chem. Soc., Vol. XL, p. 464).
By means of a separate current a spongy deposit of cadmium
is obtained from its chloride solution to which a few drops of
sulphuric acid have been added. Cadmium ammonio chloride
gives a grey non-adherent deposit, chlorine being evolved. A
similar deposit was obtained from cadmium calcium chloride.
Cadmium bromide, acidulated with weak sulphuric acid, gives
a coherent mass, susceptible of polish. If an iron wire be used
as the cathode, and a copper one as the anode, the cadmium
is deposited in long brilliant needles. A good result is also
obtained with cadmium ammonio bromide. Cadmium ammo-
nium iodid) yields a spongy mass. The sulphate gives a
coherent deposit capable of receiving a fine polish. A non-
coherent deposit was obtained from the double sulphate of
cadmium and ammonium (A. Bertrand, Jour. Chem. Soc.,
1887, Part L, p. 161). Russell and Woolrich deposited
cadmium by the electrolysis of a solution composed of cadmic
( HO)
carbonate dissolved in aqueous potassic cyanide, with free
cyanide added, and using the liquid at about 100 F. with a
cadmium anode.
For the electrolytic analysis of compounds of cadmium, see
Jour. Chem. Soc., 1877, Part I, p. 340. Also F. Beilstein, Vol.
XXXVI, 1879, pp. 276 and 746; Vol. XL., 1881, p. 1,081 ;
Vol. XLIL, 1882, p. 8,960. Watts's "Dictionary of Chemistry,"
Vol. VII., pp. 229 and 790 (E. J. Smith). Chem. News, Vol.
XXXIX., p. 185; ditto (Beilstein and Jamain), Vol. XL., p. 109;
Vol. XLIII. (E. Smith) p, 61 ; and V. Francken, Vol. XLVI.,
p. 106. Jour. Chem. Soc., Vol. XLIL, 1882, p. 1,320.
Separation of Zinc. Zn. Electro-chemical equivalent
/ K
= = 32'5. A dyad cation. Only the most highly positive
metals usually set free zinc from its solutions. From slightly
acid solutions of zinc salts magnesium deposits the metal and
hydrogen gas (Roussin, Chem. News, Vol. XIV., p. 27). Ac-
cording to S. Kern, magnesium evolved hydrogen very slowly
from a solution of zinc chloride (Jour. Chem. Soc., 1876, Part
I, p. 684). Sodium amalgam immersed in a concentrated
solution of zinc sulphate forms a viscid amalgam of zinc
(Bottger, Watts's "Dictionary of Chemistry," Vol. Ill, p. 891).
Joule also obtained amalgams of zinc by electrolysis, using a
cathode of mercury (ibid.). From an alkaline solution of a salt
of zinc aluminium easily separates the metal (A. Cossa, Watts's
"Dictionary of Chemistry," Vol. VII, p. 54). I observed
that in a solution of either nitrate, chloride, sulphate, or
acetate of zinc neither antimony, bismuth, platinum, gold,
silver, copper, brass, German silver, nickel, iron, tin, lead, or
zinc becomes coated with zinc by simple immersion. I heated
a mixture of 1-5 grain of crystals of silicon and 10'25 grains
of perfectly dry fluoride of zinc in a porcelain crucible to a
full red heat ; the salt was decomposed and zinc set free.
According to V. Eoque, wrought and cast iron previously
dipped in a strong solution of potassic carbonate became
coated with zinc by simple immersion during from three to
twelve hours in a solution composed of 1,000 parts of water,
10 of chloride of aluminium, eight of potassic bitartrate, five of
stannous chloride, four of acid sulphate of aluminium, and four
of chloride of zinc (Chem. News, Vol. XXL, p. 288).
Eaoult states that gold or copper in contact with zinc, in a
concentrated and boiling solution of chloride or sulphate (but
not nitrate) of zinc, acquires a deposit of zinc. But gold in
contact with antimony, silver, copper, nickel, iron, or lead, in
cold or boiling acid or neutral solutions of salts of zinc,
receives no such coating (Chem. News, Vol. XXVL, p. 240 ;
Vol. XXVIL, p. 59. Jour. Chem. Soc., Vol. XL, p. 464). Copper
or brass immersed in contact with zinc in a boiling saturated
( 111 )
solution of chloride of ammcnium acquires in a few minutes a
specular coating of zinc, but in a solution of cream of tartar
no such deposit occurs (E. Bottger, " Gmelin's Handbook of
Chemistry," Vol. I., p. 50; also Chem. News, Vol. XXII.,
p. 108). Copper acquires a fixed and brilliant coating of zinc
by immersing it in contact with zinc in a hot concentrated
solution of potash or soda (F. Weil, Chem. News, Vol. XIII.,
p. 2).
By means of a separate current and a zinc anode zinc has
been deposited from solutions of several of its salts, viz., the
chloride, ammonio chloride, sulphate, ammonio sulphate,
acetate, tartrate, &c. According to Smee, a solution of zinc
oxide in caustic potash is not a good conductor, the zinc anode
does not readily dissolve in it, and similarly with potassio
tartrate and potassio of cyanide.
Electrolysis of Chloride of Zine. Zn.Cl 2 . Molecular
weight = 136. Fused zinc chloride is reduced to metal by
contact with aluminium (Flavitzky, Watts's "Dictionary of
Chemistry," Vol. VIII., Part I, p. 64). It has been stated
that perfectly clean iron acquires a thin coating of zinc by
simple immersion in a solution of 30 parts of zinc chloride
and 1 of sal-ammoniac (Watts's " Dictionary of Chemistry,"
Vol. VIII., Part II., p. 1,118). According to Grove, nitride
of zinc is formed at an anode of zinc in a weak solution of
sal-ammoniac (Watts's "Dictionary of Chemistry," Vol. V.,
p. 1,072).
Electrolysis of Sulphate of Zinc. Zn.S0 4 . Molecular
weight = 161. Sodium amalgam in contact with a strong
solution of this salt forms a viscid amalgam (Bottger). Joule
formed the same compound by making mercury the cathode
in that liquid. From a solution of the sulphate, magnesium
deposits with strong action a mixture of zinc, its hydrated
oxide, and sulphate (Commaille, Chem. News, Vol. XIV.,
p. 188).
By means of a current from two Smee cells, with a large
zinc anode, a solution of one part of zinc sulphate in five to
ten parts of water may be made to yield a good deposit of
zinc. According to V. Meyer, pure zinc may be obtained
by the electrolysis of an ammoniacal solution of its sulphate
with a sheet zinc anode and a copper wire cathode (Jour. Chem.
Soc., Vol. X., 2nd Series, p. 221 ; see also Watts's "Dictionary
of Chemistry," Vol. VII., p. 1,213). %
MM. Person and Sire easily deposited zinc " on any metal,"
by the separate current process, with a single cell and a zinc
anode, from a solution of one part of oxide of zinc dissolved
in 100 parts of water containing 10 of alum (Chem. Neivs. Vol.
II, p. 275).
Electrolysis of Cyanide of Zinc and Potassium. A. Watt
makes a mixture composed of twenty gallons of distilled water,
200 ounces of cyanide of potassium, and eighty by measure of
the strongest aqueous ammonia. He then fills several large
porous cells with a solution composed of sixteen ounces of
cyanide of potassium to each gallon of water, and partly im-
merses them in the other liquid. In the porous cells he places
sheets of copper or iron to act as cathodes, and in the outer
liquid clean pieces of zinc to act as anodes, and connects the
battery in the usual way until about sixty ounces of zinc are
dissolved, and then stops the current and removes the porous
vessels. He next dissolves eighty ounces of carbonate of potas-
sium in a part of the zinc solution, and returns it to the
original portion, and stirs the mixture thoroughly. After the
sediment formed has subsided he decants the clear liquid
for use. Articles of iron may be coated in this liquid.
Anodes of zinc are employed, and a little cyanide of
potassium and liquid ammonia are occasionally added if
necessary. The battery preferred is composed of two Bunsen
cells.
Deposition of Alloys of Zine and Copper. As early as
the year 1841 M. de Kuolz deposited brass, by means of the
battery process, from a solution of the mixed cyanides of cop-
per, zinc, and potassium. One of the best solutions for yield-
ing brass by means of a separate current is that of Morris and
Pershouse. It is composed of one pound of potassic cyanide,
one of ammonium carbonate, two ounces of cupric cyanide,
and one of cyanide of zinc, dissolved in one gallon of water,
and the liquid used at 150 F., with a strong current and a
large brass anode. To increase the proportion of copper in the
deposit, either add potassic cyanide or raise the temperature, and
to increase that of the zinc, add ammonic carbonate or lower
the temperature. Walenn recommends a solution composed of
equal parts of ammonic tartrate and potassic cyanide dissolved
in water, and after addition of the cyanides of copper and of
zinc the oxides of those metals are also added to the solution.
If upon trial hydrogen is set free at the cathode, a little
ammoniuret of copper is also added to the mixture. There is
then no liberation of hydrogen, and a deposit of brass may be
obtained of any desired thickness. Two or three Smee cells
tire sufficient (Chem. News, Vol. XXL, p. 273, Vol. XXII.,
pp. 1 and 181 ; Jour. Chem. Soc., Vol. X., p. 103; Phil. Mag.,
4th Series, Vol. XLL, p. 41). In depositing from an electro-
brassing solution, which contains cyanide of potassium and
tartrate of ammonium, at a temperature but little above the
freezing point, nearly pure zinc forms upon the cathode
<Walenn, Chem. News, Vol. XXXV., p. 154; see also Watts's
"Dictionary of Chemistry," Vol. VII., p. 382).
(113)
Deposition of Alloys of Zine, Copper, and Nickel. A
solution described by Morris and Johnson for depositing German
silver is composed as follows : Dissolve one pound of potassic
cyanide and one of carbonate of ammonium in a gallon of
water. Heat the solution to 150 F. Immerse it in a large
anode of German silver and a small cathode of any suitable
metal, and pass a strong current until a large quantity of the
alloy has dissolved and a bright cathode receives a good de-
posit of the desired alloy. If the deposit becomes too red,
add ammonic carbonate; if too much of the appearance of
zinc, add potassic cyanide.
Various other mixtures for depositing brass and German
silver may be found described in works on electro-metallurgy.
For the electrolytic analysis of compounds of zinc, see Chem.
News, Vol. XXIV., pp. 100 and 172 ; Vol. XXXV., p. 264 ; Vol.
XLIIL, p. 61 ; Vol. XLIV., p. 304 ; and Vol. XLVL, p. 105.
Jour. Chem. Soc., 1877, Part I., p. 340, and Part II, pp. 804 and
924 ; Vol. XXXVIIL, 1880, p. 584 ; Vol. XL., 1881, pp. 1,081,
1,101, and 1,170; Vol. XLIL, 1883, pp. 896 and 1,320; and
Vol. XLIV., 1883, p. 122. The Chemist, New Series, Part XVIII.,,
March, 1855, p. 334. Watts's "Dictionary of Chemistry,"
Vol. VIII., Part L, p. 712.
For the electro-metallurgy of zinc see Luckow, Jour. Chem..
Soc., Vol. XLIL, 1882, p. 431 ; and the separation of zinc and
silver, by W. G. Blagden, see Watts's "Dictionary of Che-
mistry," Vol. VI., p. 1,026.
Separation of Magnesium. Mg. Electro-chemical equiva-
24-3
lent ~2- = 12 ! 15. A dyad cation. Fused magnesic chloride
is not reduced to metal by contact with aluminium (Flavitzky,
Watts's "Dictionary of Chemistry," Vol. VIII., Part L,
p. 64). An amalgam of potassium or sodium decomposes a
solution of magnesic sulphate by simple contact, and produces-
magnesium amalgam. Electrolysis of that liquid into a.
cathode of mercury also produces it (Klauer, Watts's " Dic-
tionary of Chemistry," Vol. Ill, p. 888 ; Jour. Chem. Soc., 1876,
Part I., p. 684). I melted to a perfect liquid, at nearly a white
heat, a mixture of six grains of magnesic fluoride and four of
calcic fluoride, and then added two grains of crystals of silicon.
The crystals did not dissolve, and there appeared no signs of
magnesium having been separated. The electrolytic decom-
position of the double chloride of magnesium and sodium in a
fused state by contact with sodium is the ordinary process of
obtaining the metal.
Magnesium is a very highly electro-positive metal ; it
deposits in the metallic state nearly all the base and noble
metals from solutions of their salts by simple contact. Ac-
cording to Koussin, it deposits bismuth, platinum, gold,
'( 114 )
silver, mercury, copper, lead, thallium, tin, and cadmium
(Chem. Neios, Vol. XIV., p. 27). In addition to these,
according to Phipson, it deposits nickel, cobalt, and zinc, and
even iron and manganese, from solutions of ferrous and man-
ganous salts ; but it does not deposit aluminium from its
solutions (Watts's " Dictionary of Chemistry," Vol. V., p. 795).
A sub-oxide of magnesium appears to be formed when sodic
or ammonic chloride is electrolysed with electrodes of mag-
nesium wire, the anode being covered with the black oxide
(W. Beetz, Watts's "Dictionary of Chemistry," Vol. VI,
p. 796). I have obtained this compound in a great variety
of liquids by immersing magnesium in contact with platinum
or palladium in them ; solutions of chloride and bromide of
potassium or sodium were some of the most suitable liquids
(Proceedings Birmingham Philosophical Society, Vol. IV.,
Part I.).
The metal is deposited by means of a separate current.
According to Bertrand, an adherent deposit of the metal may
be obtained by electrolysing during a few minutes a concen-
trated aqueous solution of the double chloride of magnesium
and ammonium by means of a very powerful current and a
cathode of copper (Chem. News, Vol. XXXIV., p. 227 ; Jour.
Chem. Soc., 1877, Part L, p. 161). Bunsen obtained it by
electrolysing fused chloride of magnesium at a red heat in a
deep and covered porcelain crucible, which was divided by
a vertical partition of porous porcelain extending from the
top to half way down the vessel. The current employed was
from ten zinc and carbon elements. The electrodes were of
carbon and were introduced through openings in the cover, and
the cathode was notched, so that the light melted metal col-
lected in the notches, instead of rising to the surface and then
burning. Matthiessen states that the metal may be much
more easily obtained by this method if the salt employed con-
sists of a mixture of four molecules of magnesic chloride, three
of chloride of potassium, and a little chloride of ammonium.
In this case, the liquid salt being lighter than the magnesium,
the latter falls to the bottom (Watts's "Dictionary of Chemis-
try," Vol. II. p. 438 ; Vol. Ill, p. 751).
For the use of electrolysis in the metallurgy of magnesium,
see F. Fischer, Jour. Chem. Soc., Vol. XLIV., 1883, p. 399.
Separation of Thorium. Atomic weight = 233'9. Sodium
sets free metallic thorium from fused double chloride of .thorium
and potassium in an iron crucible (L. F. Nilson, Jour. Chem.
Soc., Vol. XLIV., 1883, p. 152).
Separation of Norwegium. Atomic weight = 145-9 (?).
According to Dr. Tellef, the sulphate solution of this metal is
turned brown on the addition of zinc, and the metal ia
deposited in the pulverulent state (Chem. News, Vol. XL.,
p. 25).
Separation of Cerium. Ce. Atomic weight = 94-2.
Lanthanum. La. Atomic weight = 9 2. And Didymium. Dy.
Atomic weight = 96. Crude double chloride of cerium and
potassium in a fused state at a red heat is decomposed by
metallic sodium, and metallic globules of impure cerium, to-
gether with shining scales of an oxychloride of cerium, are
obtained (Wohler, Watts's " Dictionary of Chemistry," Vol.
VI., p. 419).
When a mixture of oxide of cerium and potassic fluoride is
melted in a porcelain crucible, and subjected to electrolysis,
potassium and silicide of cerium in the form of a brown mass
are deposited upon the cathode (Ulik, Watts's " Dictionary of
Chemistry," Vol. V., p. 266 ; and Vol. VL, p. 420).
According to Bunsen, either of these metals may be separated
by electrolysis with a separate current in the following man-
ner : Its chloride is mixed with sal-ammoniac (both as dry as
possible), and the mixture heated to redness in a platinum
crucible to expel all the sal-ammoniac. A porous clay vessel
of the best quality is filled with the residue, then placed in a
Hessian crucible, surrounded by a cylinder of sheet iron (with
a long projecting strip for connection) to serve as the anode,
and the space between the two vessels filled with a previously
melted mixture of an equal number of equivalents of the
chlorides of potassium and sodium. A thick iron wire, enclosed
in a clay pipe, has a coil of very fine iron wire at its extremity
to serve as the cathode, and is immersed in the fused salt in
the inner vessel. The fusion is effected by preference in a
fire of glowing charcoal, to prevent as far as possible the pre-
sence of aqueous vapour, and a strong current is employed
(Electrical News, Vol. I., p. 184 ; see also Hillebrand and Norton,
Watts's "Dictionary of Chemistry," Vol. VIII., pp. 420-421).
T. Schuchardt states that he has succeeded in obtaining by
electrolysis metallic cerium in globules weighing from four to
five grammes ; and that he has also by the same process, with
the aid of a current from six Bunsen cells, obtained metallic
didymium in globules the size of a pea (Chem. News, Vol. XL,,
p. 35). Hillebrand and Norton also state that they have
obtained each of these metals by means of electrolysis (Jour.
CliemSoc., 1876, Part II., p. 276).
According to C. Erk, the electrolysis of a neutral solution
of cerous nitrate by means of a current from three Bunsen
cells yielded at the cathode a brownish-yellow mass and a
quantity of ammonia sufficient to precipitate the whole of the
cerium. A concentrated one of cerous chloride gave free
chlorine at the anode and a deposit of ceroso-ceric hydrate at
the cathode. The same salt in a state of fusion, with an anode
i 2
of gas-carbon, gave small quantities of metallic cerium, and
reddish white laminae of cerium oxychloride at the cathode ;
and at the anode hydrochloric acid was evolved, and a large
quantity of ceroso-ceric oxide formed. Strong solutions of
cerous sulphate became yellow at the anode from formation
of ceroso-ceric sulphate, and at the cathode yielded a little
metallic cerium and a waxy deposit of ceroso-ceric sulphate,
which subsequently became crystalline. An aqueous solution
of cerous acetate yielded a basic acetate (Watts's " Dictionary
of Chemistry," Vol. VII., p. 274).
Separation of Gallium. Ga. Atomic weight = 69-86.
Gallium is allied to aluminium and also to mercury. Cad-
mium separates gallium in the metallic state from a boiling
solution of its chloride by prolonged immersion (M. Lecoq de
Boisbaudran, Jour. Chem. Soc., Vol. XLII., 1882, p. 897). So
long as the liquids are sensibly acid, and the evolution of
hydrogen goes on actively, zinc does not precipitate either the
chloride or sulphate of gallium ; but when the liquids become
basic, and hydrogen is evolved but slowly, either the oxide or
a subsalt of gallium separates in white flakes mixed with
subsalts of zinc (M. Lecoq de Boisbaudran, Chem. Neivs,
Vol. XXXV., p. 158).
On passing a current from five bichromate cells through an
ammoniacal solution of sulphate of gallium, with platinum
electrodes, metallic gallium is deposited on the cathode, and a
white film is formed upon the anode. In four and a-half hours
the metallic deposit weighed -0016 gramme. With ten cells,
in five hours it weighed '0034 gramme. The metal was
adhesive, not easily burnished by friction, but better by pres-
sure (Lecoq de Boisbaudran, Jour. Chem. Soc., 1876, Part L,
p. 521 ; Chem. News, Vol. XXXV., p. 150).
According to Schicht, by electrolysis, gallium, like zinc, is
deposited completely and in a pure state upon the cathode
(Chem. News, Vol. XLL, p. 280). By the electrolysis of a
solution of oxide of gallium in one of caustic potash, by means
of a current from five or six Bunsen's cells, and platinum
electrodes, metallic gallium is deposited as liquid globules
(M. Lecoq de Boisbaudran, Chem. News, Vol. XXXV., pp. 150
and 168).
Separation of Aluminium. Al. Electro-chemical equiva-
27*5
lent= ^-~- = 9-16. A triad cation. Magnesium by simple
immersion in solutions of aluminium salts produces aluminic
hydrate (S. Kern, Chem. News, Vol. XXXIII., p. 236). Mag-
nesium does not deposit aluminium as metal from its solutions
(Roussin, Chem. Neics, Vol. XIV., p. 27). An amalgam of
aluminium is formed by contact of the metal with sodium
( "V )
amalgam and water (Watts's " Dictionary of Chemistry,"
Vol. III., p. 886).
Various persons have stated that aluminium cannot be
deposited by the aid of a separate electric current. "The
electrolytic reduction of aluminium may be performed either
in the wet or in the dry way. The reduction from the fused
chloride of aluminium and sodium was first effected by Bunsen
in 1854. The salt is introduced in a fused state into a red-
hot porcelain crucible, divided into two parts by a porous
earthenware diaphragm, and the extremities of the poles of a
Bunsen battery of ten elements are introduced into the two
halves of the fused mass. The metal is then reduced at the
cathode, and if the temperature is sufficiently high the metal
is melted into globules " (Watts's " Dictionary of Chemistry,"
Vol. L, p. 152).
M. H. St. Claire Deville says : " It appeared to me impos-
sible to obtain aluminium by the battery in aqueous liquids.
I should believe this to be an impossibility if the brilliant
experiments of M. Bunsen on the production of barium did
not shake my conviction. Still, I may say that all processes
of this description which have recently been published for the
preparation of aluminium have failed to give me good results.
It is of the double chloride of aluminium and sodium, of which
I have already spoken, that this decomposition is effected.
The bath is composed of two parts by weight of chloride of
aluminium, with the addition of one part of dry and pulverised
common salt; the whole is mixed in a porcelain crucible,
and heated. The combination is effected with disen-
gagement of heat, and a liquid is obtained which is very
fluid at 392 F., and fixed at that temperature. It is intro-
duced into a vessel of glazed porcelain, which is to be kept at
a temperature of about 329F. The cathode is a plate of
platinum on which the aluminium (mixed with common salt)
is deposited in the form of a greyish crust. The anode is
formed of a cylinder of charcoal, placed in a perfectly dry
porous vessel, containing melted chloride of aluminium and
sodium. (The densest charcoal rapidly disintegrates in the
bath, and becomes pulverulent; hence the necessity of the
porous vessel.) The chlorine is thus removed with a little
chloride of aluminium proceeding from the decomposition of
the double salt. This chloride would volatilise and be entirely
lost if some common salt were not in the porous vessel. The
double chloride becomes fixed, and the vapours cease. A
small number of voltaic elements (two are all that are abso-
lutely necessary) will suffice for the decomposition of the
double chloride, which presents but little resistance to the
electricity. The platinum plate is removed when it is suffi-
ciently charged with the metallic deposit. It is suffered to
cool, the saline mass is rapidly broken off, and the plate
( US)
replaced" (The Chemist, New Series, No. XIII., October, 1854,
p. 12). By the electrolysis of fused sodic aluminic chloride
the aluminium deposited contains silicium derived from the
charcoal electrodes (Deville, Watts's " Dictionary of Chemistry,"
Vol. L, p. 152, and Vol. V., p. 267).
According to A. Bertrand, by means of a separate current
aluminium is deposited on a copper plate in granules from
aluminium ammonium chloride, whilst chlorine is evolved at
the anode (Jour. Chem. Soc., 1877, PartL, p. 161; Chem.Neivs,
Vol. XXXIV., p. 227). M. Corbelli deposits the metal by
electrolysing a mixture of rock alum, or sulphate of aluminium,
and the chlorides of calcium or of sodium, the anode being
formed of iron wire coated with an insulating material, and
dipping into mercury placed at the bottom of the solution, and
the cathode of zinc immersed in the solution. Aluminium is
then deposited upon the zinc, and the chlorine which is
eliminated at the anode unites with the mercury and
forms calomel (Watts's "Dictionary of Chemistry," Vol. I,
p. 152).
Thomas and Tilley state that they deposit aluminium from
a solution composed of freshly precipitated alumina dissolved
in boiling water containing cyanide of potassium ; also from a
solution of calcined alum in aqueous cyanide of potassium,
and from several other liquids. They also state that they
have deposited alloys of aluminium and silver; aluminium,
silver, and copper ; aluminium and tin ; aluminium, silver, and
tin; aluminium and copper; aluminium and nickel; aluminium
and iron, &c. J. B. Thompson says that he has for more than
two years been depositing aluminium on iron, steel, and other
metals, at a temperature of about 500 F., and also depositing
aluminium bronze of various tints from the palest yellow to
the richest gold colour (Chem. News, Vol. XXIV., p. 194).
Jeancon deposits the metal from an aqueous solution of a
double salt of aluminium and potassium of specific gravity
1-161, at a temperature of 140 F., by means of a current
from three Bunsen cells (Telegraphic Journal, Vol. I., p. 308).
T. Ball also deposits it from the double chloride of aluminium
and potassium (Chem. News, Vol. V., p. 153).
I electrolysed a strong solution of aqueous fluoride of
aluminium, containing free hydrofluoric acid, with large sheet
platinum electrodes and a strong current. Gas was evolved
freely from the anode, and the liquid became heated.
Aluminium used as an anode in dilute sulphuric acid largely
stops the current, probably by becoming coated with a layer
of insulating oxide ; but if employed only as a cathode it is
not thus effected (Chem. News, Vol. XXXL, p. 99 ; Telegraphic
Journal, Vol. Ill, p. 59).
It may be superficially coated with mercury by being made
the cathode in contact with mercury in acidulated water
(Cailletet, Comptes Eendus, XLIV., p. 1,250; also Watts'a
"Dictionary of Chemistry," Vol. VII., p. 54).
Aluminium, like magnesium, has great power in reducing
metallic solutions and depositing their metals by simple im-
mersion process ; it reduces those of silver, mercury, copper,
lead, thallium, and zinc (see A. Cossa, Watts's "Dictionary
of Chemistry," Vol. VII., p. 54).
For the use of electrolysis in the metallurgy of aluminium,
see F. Fischer, Jour. Chem. Soc., Vol. XLIV, 1883, p. 399.
For the electrolytic analysis of compounds of aluminium, see
V. Francken, Chem. News, Vol. XLVL, p. 106; also Jour.
Chem. Sue., Vol. XLIL, 1882, p. 132 ; and A. Claessen, ibid.,
p. 89G.
Separation of Glucinura. Gl. Atomic weight = 9 -3. A
cation. Nilson and Petterson were unable to separate this metal
by the separate current method (Chem. News, Vol. XXXVIL,
p. 195). Becquerel deposited the pure metal from a concen-
trated solution of its chloride by means of a current from
twenty voltaic cells. It was in the form of brilliant, steel
grey crystalline lamina} (Gmclin, " Handbook of Chemistry,"
Vol. III., p. 293).
For the electrolytic analysis of its compounds, see A. Claes-
sen, Jour. Chejn. Soc., Vol. XLIL, 1882, p. 89G.
Separation of Calcium. Ca. Atomic weight ^= 40. Accord-
ing to Klauer, calcium amalgam may be formed either by
simple immersion of sodium amalgam in solutions of calcium
salts, or by passing a strong electric current from those liquids
into mercury, llerschel observed that during the electrolysis,
of a solution of calcic chloride by means of a separate current,
the cathode evolved gas and became coated with caustic lime.
This metal was first separated by an electric current during
the year 1808 by Sir 11. Davy, who obtained it as an amalgam
by employing a cathode of mercury. Fremy subsequently
electrolysed pure calcic fluoride in a fused state in a platinum
crucible. Brisk effervescence occurred in the mass, a gas was
set free at the anode, metallic calcium was deposited upon the
cathode and became converted into lime by the oxygen of the
air. It was difficult to make the observations, and the crucible
was soon alloyed and perforated by the action (The Chemist,
New Series, Vol. II., p. 5-18).
Matthiessen electrolysed a fused mixture of two molecules
of calcic and one of stroutic chloride with a small amount of
sal-ammoniac in a porcelain crucible. The anode was of gas
carbon, and the cathode was formed by winding a thin iron
wire round a thicker one and dipping its end only just into
the liquid. The calcium was set free as metallic globules
upon the thin wire. He states that the metal deposited upon the
cathode by a separate current in a fused mixture of chloride
( 120)
of calcium and the chlorides of potassium or sodium is not
calcium (Watts's "Dictionary of Chemistry," Vol. I., p. 715).
Bunsen deposited calcium in a similar manner to that
employed for manganese (see paragraph on " Separation of
Manganese "), except that he used a greater density of current.
He acidulated a concentrated and boiling hot solution of the
chloride with hydrochloric acid, poured the boiling liquid into
the porous cell, and employed as a cathode an amalgamated
platinum wire. The calcium was deposited as a grey layer upon
the amalgamated surface. The process is difficult, because the
calcium quickly oxidizes to a layer of lime, which covers the
cathode and stops the current. The deposit must be frequently
removed, and the wire freshly amalgamated each time before
re-immersion ; and even then but a small amount of the metal
is obtained (The Chemist, New Series, Vol. I., Part II., p, 686,
August, 1854).
Separation of Strontium. Sr. Atomic weight = 87*5.
A cation. Solutions of salts of strontium are slowly decom-
posed by simple immersion of metallic magnesium ; after two
days they yield a white deposit of strontium hydrate (S. Kern,
Chem. News, Vol. XXXIIL, p. 112; Jour. Chem. Soc., 1876,
Part I., p. 684). Sodium amalgam decomposed a saturated
solution of chloride of strontium with formation of strontium
amalgam (Watts's "Dictionary of Chemistry," Vol. III., p. 886 ;
see also Vol. VIIL, Part II., p. 1,829). Silicon does not sepa-
rate strontium from heated fluoride of strontium. I heated
to redness a mixture^ of the two substances, but no chemical
change occurred. Caron deposited the metal by fusing its
chloride with an alloy of sodium with tin or lead ; the reduc-
tion was not effected by sodium alone (Watts's " Dictionary of
Chemistry, Vol. V., p. 436). Strontium is electro-positive to
magnesium, but not to potassium or sodium, in water.
Sir H. Davy was the first to deposit this metal by means of
a separate current. He formed into a cup a pasty mass of
strontium carbonate with water, placed the cup upon a plati-
num dish, and filled the cup with mercury as the cathode.
By passing a current from 300 voltaic cells from the platinum
to the mercury the strontium was deposited upon and absorbed
by the mercury. Hare obtained the metal in a similar manner
(Watts's "Dictionary of Chemistry," Vol. V., p. 436).
Bunsen obtained strontium in a precisely similar way to
that of obtaining manganese (see ante), using a salt of stron-
tium instead of one of that metal (Watts's "Dictionary of
Chemistry," Vol. II., p. 437). Matthiessen obtained it from
the fused chloride in the following manner : A small porous
cell was placed in a porcelain crucible, and both vessels nearly
filled with anhydrous chloride of strontium, the level of that
in the porous coll being the highest. The salt was melted so
that a crust appeared on its surface. The cathode consisted of
a thick iron wire, enclosed in the stem of a tobacco pipe, so
that only l-20th of an inch of it projected at the lower end,
round which a very thin iron wire was coiled. The anode was
a cylinder of sheet iron placed in the outer space. The cathode
was immersed in the inner vessel, and the current passed ; the
metal collected upon it beneath the crust (Watts's " Dictionary
of Chemistry," Vol. IL, p. 438).
Separation of Barium. Ba. Atomic weight = 137. A
cation. Sodium amalgam separates this metal from a saturated
solution of barium chloride at 93 C., and forms an amalgam
(Crookes, Chem. News, Vol. VI, p. 194; Watts's "Dictionary
of Chemistry," Vol. VI, pp. 252, 253).
Barium amalgam may be prepared electrolytically either by
depositing barium into mercury, or by contact of sodium
amalgam with solutions of chloride of barium. It is a soft,
pasty substance, somewhat gritty (Cailletet, Watts's " Dic-
tionary of Chemistry," Vol. III., p. 886).
Sir H. Davy was the first to deposit barium by means of a
separate current. He employed a wet mass of barium hydrate,
carbonate, chloride, or nitrate, a cathode of mercury, and a
powerful current from 500 voltaic cells, and obtained the
metal as an amalgam with the mercury. Hare prepared it in
a similar manner from the chilled and moistened chloride by
means of a current from 100 cells (Watts's " Dictionary of
Chemistry," Vol. I., p. 500). Bunsen electrolysed a boiling
hot concentrated and acidulated solution of chloride of
barium in a similar way to the one he employed in obtaining
manganese, chromium, and calcium. It was more easily ob-
tained than calcium (see ante ; also The Chemist, New Series,
Vol. L, p. 686; Watts's "Dictionary of Chemistry," Vol. I,
p. 500). Matthiessen obtained barium from its fused chloride
in a similar manner to that in which he obtained strontium (see
ante ; also Watts's " Dictionary of Chemistry," Vol. II., p. 438).
A solution of barium nitrate, electrolysed with platinum
electrodes, yielded nitric acid at the anode and caustic baryta
at the cathode (Sir H. Davy).
Separation of Lithium. Li. Electro-chemical equiva-
lent 1. A monad cation. I observed that lithium was not
separated by adding crystals of silicon to a fused mixture of
the fluorides of lithium and sodium, nor were the crystals cor-
roded or altered in weight. I also fused some fluoride of
lithium in an open platinum crucible within a partially covered
clay muffle, and electrolysed it by means of a current from six
Smee elements, and two flat platinum wire helices as elec-
trodes, during thirty minutes. The conduction was free, and
much gas was evolved from the anode only all the time. The
anode was not corroded. A small amount of lithium was
( 122 )
deposited upon the platinum cathode, and alloyed with it. By
electrolysing a larger mass of the salt, with a current from
six Grove cells and a thick platinum wire cathode enclosed
within, but insulated from a platinum tube, to exclude the air
from contact with the deposited lithium, the action was
copious ; with a gold anode the gold was corroded freely, and
particles of it in large quantity floated in the liquid and united
the electrodes. The cathode swelled greatly, and its lower end
bent itself towards the anode, became quite grey in colour, and
split in the direction of its length.
Bunsen was the first person who electro-deposited this metal
(Watts's "Dictionary of Chemistry," Vol. III., p. 727). By
electrolysing fused chloride of lithium with a current from
four or six Bunsen cells, an anode of gas coke, and a cathode
of iron wire, he deposited silver white metal upon the wire
(Watts's "Dictionary of Chemistry," Vol. II., p. 437). Schnitzler
also electrolysed a mixture of the fused chlorides of lithium
and ammonium by a current from twelve Bunsen cells, and a
cathode of iron wire, and obtained a metallic lithium (Jour. Chem.
Soc., Vol. XXIL, p. 9G1).
Separation of Sodium. Na. Electro-chemical equivalent
= 23. A monad cation. In a solution of sodic chloride, mag-
nesium evolves hydrogen slowly, sodium hydroxide being
formed, rendering the solution alkaline (S. Kern, Jour. Cliem.
Soc.j 1876, Part I., p. G84). Beetz observed that under these
conditions a black suboxide of magnesium is formed. Carbon,
also iron, reduces the melted hydrate or carbonate of sodium
at a high temperature, and sets free the metal.
Sir H. Davy first electro-deposited sodium in the year 1807
by moistening its hydrate with water in a platinum capsule
which acted as the anode, dipping a platinum wire cathode in
the salt, and using a current from a battery composed of 100
to 200 cells. He also deposited it more easily into mercury
in a similar way to that already described under magnesium,
and thus obtained an amalgam of the two metals.
In the electrolysis of melted sodic hydrate an anode of
either platinum, silver, or copper dissolves in the liquid, and
the respective metals are deposited upon the cathode (A.
Brester, Chem. News, Vol. XVIL, p. 145).
Electrolysis of Sodie Fluoride. Na.F. Molecular weight
= 42. I have noticed that crystals of silicon thrown into
melted fluoride of sodium evolved bubbles of vapour, which
exploded and burned with a yellow flame on arriving at the
surface of the liquid. In a second trial, 7 grains of the dry
fluoride in powder mixed with one grain of the crystals were
heated to redness; the crystals lost -15 grain in weight. I
electrolysed a saturated aqueous solution of sodic fluoride by
a current from six Grove cells with platinum electrodes; gas
( 123 )
was evolved from the anode, and emitted a powerful odour
of ozone.
Electrolysis of Sodie Chloride. Na.Cl. Molecular weight
= 58-5. Hisinger and Berzelius electrolysed a solution
of common salt with silver electrodes. Gas was evolved at
the cathode, and after a time at the anode also. The anode
became covered with argentic chloride, the liquid near it con-
tained dissolved chlorine, and the solution near the cathode
contained free soda. With lead electrodes the negative wire
evolved gas, and received a deposit of crystals of lead, and the
anode became coated with plumbic chloride. By electrolysing
a solution of common salt, Higgins and Draper observed that
chlorine was set free at the anode, and hydrogen gas and soda
at the cathode. But if the cathode consisted of mercury
sodium amalgam was produced. According to Matthiessen,
a fused mixture of the chlorides of calcium and of sodium
yields a deposit of the latter metal, when electrolysed in a
certain manner (Watts's " Dictionary of Chemistry," Vol. I,
p. 715).
Electrolysis of Sodium Carbonates. Na 2 C0 3 and Na
HC0 3 . According to Favre and Roche, by electrolysis, neutral
sodium carbonate splits up into CNa.0 3 and Na, the sodium
being oxidized by the water with separation of hydrogen.
The acid carbonate is resolved into Na and CH0 3 , the sodium
being then oxidized and hydrogen evolved ; the 2CH0 3 is
then resolved into 2C0 2 + H 2 + 0. According to Burckhard^
sodic carbonate in a state of fusion is a good conductor, and is
decomposed by electrolysis into carbonic acid at the anode,
and soda together with a little carbon at the cathode (Chem.
News, Vol. XXL, p. 238).
Electrolysis of Biborate of Sodium. Fused borax yields
oxygen gas at the anode and baron at the cathode. The
boron is separated by indirect action ; the current resolves the
soda into oxygen and sodium, and the latter separates boron
from the boracic acid (Faraday, Gmelin's " Handbook of Che-
mistry," Vol. I., p. 460). Burckhard states that fused borax
conducts, suffers electrolysis, and a series of compounds are
formed or volatilised ; but the chief result is that the salt is de-
composed into soda and boron at the cathode and oxygen at
the anode (Chem. News, Vol. XXI., p. 238).
Electrolysis of Sodic Sulphate. Na 2 S0 4 . Molecular
weight = 140. By the electrolysis of this salt in a fused state
with platinum electrodes, sodium is deposited and combines
with the cathode (Brester, Chem. News, Vol. XVIII., p. 154).
From the results obtained by electrolysing sulphide of
sddium. Buff concluded that all the sulphur travelled to
( 124)
the anode and the sodium towards the cathode (Chem. Neios,
Vol. XV., p. 279).
Electrolysis of Diphosphate of Sodium. Na 2 HP0 4 . A
solution of this substance is decomposed by a separate current
into phosphoric acid at the anode and soda at the cathode.
According to Faraday, acid phosphate of sodium in a state of
fusion yields hydrogen at the cathode (Gmelin, " Handbook
of Chemistry," Vol. I., p. 460). According to Burckhard, fused
pyrophosphate of sodium, electrolysed with platinum elec-
trodes, yields -phosphide of platinum; but the chief result is
that the salt splits up into oxygen, phosphorus, and soda
(Chem. News, Vol. XXI, p. 238). ^ '
For the reducing action of sodium amalgam on solutions of
silver, mercury, iron, and chromium, see the sections relating
to thofe metals; also AVatts'a "Dictionary of Chemistry,"
Vol. VI., p. 816. For Jablochkoff's process of making sodium
by electrolysis, see Scientific American, Sept. 22, 1883, p. 643.
Separation of Potassium. K. Electro-chemical equiva-
lent =39*1. A monad cation. Magnesium, by simple immer-
sion in a solution of potassic dichromate, forms potassic
hydroxide (S. Kern, Jour. Chem. Soc. t 1876, Part II., p. 479).
Zinc amalgam immersed in a solution of caustic potash libe-
rates pure hydrogen (Watts's "Dictionary of Chemistry,"
Vol. III., p. 891). According to W. Skey, an aqueous solu-
tion of potassic chloride becomes alkaline by contact either
with zinc or with silver, in the first case, probably by decom-
position of water and formation of ammonia, aided by for-
mation of zinc oxide, and in the second by oxidation of the
silver by free oxygen, and the subsequent decomposition of
that oxide with formation of silver chloride and caustic
potash (Jour. Chem. Soc. t 1876, Part II, p. 266). Both carbon
and iron separate potassium from melted potash at a white
heat, and the process for obtaining potassium is based upon
this fact. Brester states that even silver will dissolve in large
quantities in melted potassic hydrate (Chem. Ntws, Vol. XVIIL,
p. 145), and I have observed that when this hydrate is melted
in a pure silver crucible the vessel loses in weight.
Electrolysis of Potassie Hydrate. KHO. Molecular
weight = 56'1. Potassium was lirst separated by electrolysis
in the year 1807 by Sir H. Davy. He moistened a piece of
potassic hydrate with water, placed it in a platinum capsule,
which acted as a cathode, and touched the hydrate with the
platinum wire anode of a battery of from 100 to 200 of Wol-
laston's cells. The potash liquefied, and globules of the metal
separated at the cathode. Since that time it has been found
that even a feeble voltaic current will liberate potassium from
aqueous solutions of some of its salts, and if the deposited
( 125 )
metal is protected from oxidation by being deposited into a
cathode consisting of a large bulk of mercury with but a small
portion of its surface exposed to the liquid, the potassium can
be obtained in the form of its amalgam.
When mercury is placed in a cup connected with the cathode
of a voltaic battery of at least 20 pairs, and covered with a
strong solution of caustic potash, in which a piece of that sub-
stance is immersed, and into which the anode dips, the mercury
takes up potassium (Berzelius, Watts's "Dictionary of Che-
mistry," Vol. Ill, p. 889).
According to Janeczek, when melted potash is electrolysed
oxygen is evolved at the anode and potassium at the cathode,
bit no hydrogen ; but if the experiment is made in a closed
apparatus, after some time ifc is found that water is evolved
with the oxygen, and some hydrogen is also set free ; the
latter probably results from the action of the potassium upon
the melted alkali (Jour. Chem. Soc. t 1876, Part L, p. 182 ; also
Watts's "Dictionary of Chemistry," Vol. VIII., Part I,
p. 709).
Brester states that in the electrolysis of melted caustic
potash an anode of either platinum, silver, or copper dissolves
in the liquid, and the respective metals are deposited upon the
cathode (Chem. News, Vol. XVIIL, p. 145).
Electrolysis of Potassie Nitrate. KN0 3 . Molecular
weight =101-1. Some information has already been given of
the effects of an electric current upon this compound (see
"Electrolysis of Oxides of Nitrogen"). According to Fara-
day, an aqueous solution of it conducts electricity very easily,
and yields hydrogen at the cathode.
Electrolysis of Potassie Fluoride. KF. Molecular
weight = 58-1. Fremy electrolysed fused potassic fluoride,
and obtained a gas which rapidly attacked platinum, decom-
posed water, with formation of hydrofluoric acid, and dis-
placed iodine from metallic iodides (Watts's " Dictionary of
Chemistry," Vol. II., p. 673). The following are experiments
of mine made with this substance : I fused 130 grains
of ths pure salt in a platinum crucible within a partially
covered clay muffle inserted in the hole in the top of a small
gas furnace, and electrolysed it during two and a-half hours,
by means of a current from six Smee cells, and two flat
helices of platinum wire as electrodes. There was free con-
duction and much gas (of an odour like that of hydrofluoric
acid) evolved from the anode, but none from the cathode,
and no signs of any deposit. The anode was not cor-
roded, nor altered in weight. I also electrolysed some of
the same salt in a state of fusion by means of a current from
six Grove cells with a thick platinum wire as the anode
and the platinum vessel as the cathode. Great heat was
( 126 )
evolved, and violent electrolytic action occurred ; nearly white
hot metallic globules also accumulated and exploded re-
peatedly. The end of the anode fused, and particles of
platinum ramified from it in white hot threads, and a short
electric arc (about 1-1 Oth of an inch in length) was produced.
I also perfected and used a somewhat elaborate platinum
apparatus, by means of which the gas from the anode was
prevented from coming in contact with the cathode, and
might be collected, the electrodes being enclosed within (but
isolated from) two wide platinum tubes. One thousand
grains of the perfectly pure salt were electrolysed in this
apparatus by means of a current from six Grove cells. The
anode, which was a solid rod of platinum, was rapidly cor-
roded, and was thus cut off at the level of the liquid and
stopped the current ; the corroded surface was very bright, as
if fused potassium was deposited upon the cathode. Much
spongy platinum was diffused in the melted salt, and the
apparatus was a little corroded at the surface of the liquid.
No gas was evolved at the anode. The deposited potassium
did not alloy with the stout rod of platinum used as the
cathode. 55'35 grains of grey metallic platinum were found
in the saline mass ; a salt of platinum appeared to have been
formed at the anode, then dissolved or diffused throughout
the liquid and decomposed by the heat, and thus the liberated
fluorine did not escape at the anode, but was evolved in the
mass of the liquid generally, and came into contact with the
liberated potassium.
Having ascertained the electrical relations of palladium,
gold, platinum, and indium in the fluoride, palladium being
the most positive and indium the most negative, I repeated
the experiments with an anode of iridium and a current from
three Grove cells. Copious clouds descended at once from
the anode, and made the liquid opaque ; there was also a
violent action at the anode. The anode became black, and a
little gas was evolved from it, accompanied by an acid odour
like that of a mixture of sulphurous anhydride and hydro-
fluoric acid. Potassium was freely liberated at the cathode,
and produced occasional explosions. With a current from
six cells the anode dissolved rapidly, and soon lost thirty-
eight grains. I then put a pure gold anode, and employed
two cells. Gas, of a feebly acid odour, was freely evolved at
the anode ; and with a current from six cells was very copious,
and smelt much like sulphurous anhydride. The gold dis-
solved much less rapidly than the iridium. With a palladium
anode and a current from six cells the anode rapidly dissolved,
potassium was deposited and exploded frequently, and an
odour like that of hydrofluoric acid was strong, much gas
being liberated ; 33 '3 grains of free metal were found in the
saline mass. The platinum cathode was not corroded.
(127)
In the experiments the platinum anode dissolved, as if
melted ; the iridium one was black, the palladium one was
oxidised of various colours. The platinum vessel was cut
into at the level of the surface of the liquid, evidently not
by the fused fluoride of potassium, but by some substance set
free at the anode by electrolysis. In another instance I electro-
lysed the pure fused fluoride with a large platinum anode, small
platinum cathode, and a current from three Grove cells during
half an hour. Much gas, having an odour of ozone and hydro-
fluoric acid, was evolved from the anode, and the latter dis-
solved rapidly and lost 37*5 grains in weight. The gas
reddened test paper. The platinum containing vessel was
corroded at the line of surface of the liquid, and lost about
eleven grains. About fifty-one grains of free metallic platinum
in loose powder were found in the saline residue. Each of
these experiments shows that a very corrosive substance was
liberated at the anode.
I electrolysed the fused salt with a gas carbon anode and
a platinum wire flat helix as a cathode with a current from
six Smee cells. Free conduction occurred, and much gas was
set free from the anode only. The part of the anode in the
liquid was not visibly corroded.
I also electrolysed about Soz. of pure double fluoride of
hydrogen and potassium (KF HF) in a fused state during half
an hour, at about 300 F., with a current from ten Smee
cells, and electrodes of stout sheet platinum. There was
copious conduction, and abundance of hydrogen evolved at
the cathode, but no gas from the anode, which was rapidly
corroded away, with a rough surface, and lost 9*37 grains.
The salt became less fusible by loss of hydrofluoric acid, which
escaped freely all the time. The saline residue contained a
small amount of dissolved platinum salt, and nearly 9 grains
of free metallic platinum. In a second experiment, lasting
half an hour, the salt was kept only just fused, and a small
gold anode was employed. The conduction was free, and
much gas was evolved from the cathode, and a film of bright
yellow gold spread over the surface of the salt, and connected
the electrodes, unless the liquid was continually stirred. The
anode rapidly dissolved (more quickly than that of platinum),
and the salt of gold at once decomposed, and set free finely-
divided gold as a dull, red-brown powder at the anode. No
gas appeared at the anode at any time ; that from the cathode
detonated on applying a light. There was loose red-brown
powder of gold, weighing 1-4 grain, upon the cathode, but of
adherent gold only -05 grain. The anode was corroded, and
lost 6-80 grains. The saline residue contained no dissolved gold,
but 5 '85 grains of red-brown powder, containing 5'30 grains of
gold.
In a third similar experiment, by using a large sheet
(128)
platinum anode and a small platinum cathode, and a current
from ten Smee cells during two hours, the phenomena were
the same as in previous experiments. The anode lost 28
grains ; much loose platinum collected on the cathode, which
was neither corroded nor alloyed. The saline residue con-
tained a trace of dissolved platinum salt, and nearly all the
corroded platinum in a metallic state. In a fourth experiment
I continued the action during three and a-half hours ; the re-
sults were as before. The loss of the anode was 35 '7 3 grains.
The saline residue contained a small quantity of dissolved
double fluoride of platinum and potassium, which, after being
well washed, was dried and heated to redness ; it then shot
about as if gas was evolved from it. In a fifth similar ex-
periment, lasting four and a-half hours, at the lowest possible
fusion temperature, more of the brown platinum salt formed
at the anode and dissolved in the liquid. The anode lost
G4*81 grains. In a last experiment I electrolysed a gently
fused mixture of 900 grains of the pure double salt and
100 grains of pure argentic fluoride, with a large anode of
platinum and a large cathode of silver. Conduction was
complete with ten Smee cells. No gas was evolved at either
electrode. The surface of the anode disintegrated rapidly
and lost 49*84 grains in four and a-half hours' action. The
separated platinum dissolved only to a small extent in the
liquid, and subsided in admixture with the silver to the bottom-
of the vessel as a fine, black powder, weighing 7 3 -9 3 grains,
which lost less than two per cent, when heated to redness.
Some grey silver powder was deposited upon the cathode. In
all these experiments with the acid fluoride, saline films con-
tinually formed upon the surface of the liquid. They came
from the cathode and were more abundant the deeper the
cathode was immersed.
I electrolysed a nearly saturated aqueous solution of pure
fluoride of potassium by means of a current from six Grove
cells with large platinum electrodes. Conduction was copious,
and the liquid acquired a nearly boiling temperature. Much
gas, having an odour like that of a mixture of ozone and
chlorine, was evolved at the anode. A saturated solution of
the same salt, electrolysed by a current from ten large Smee
cells with large platinum electrodes, evolved gas at each elec-
trode. That from the anode smelt powerfully of ozone, and
reinflamed a red hot splint. Several other experiments with
variations in the size of the electrodes were made, and with
addition of hydrofluoric acid, but the results were similar.
I saturated some pure dilute hydrofluoric acid of 40 per
cent, at 60 F. with pure double fluoride of hydrogen and
potassium, and electrolysed the solution by a current from ten
Smee cells, a gold anode, and a platinum cathode, during 5J
hours. Gas was evolved freely from both electrodes, and a
( 129)
strong odour of ozone was observed. The anode lost 1*73
grain, and the cathode acquired first a gilded appearance and
then a black coating, and the liquid became black with finely
divided matter.
Electrolysis of Potassie Chloride. KC1. Molecular weight
= 74*6. Matthiessen separated the metal from this salt by
means of a current from six Bunsen's elements with carbon
electrodes. He melted a dry mixture of one molecular weight
of potassic chloride and one of calcic chloride, arranging the
distribution of the heat so that a little of the mixture remained
unfused around the upper part of the cathode. Chlorine
escaped at the anode, and pure potassium accumulated around
the anode beneath the crust. The crucible was then cooled,
and its contents removed under rock oil (Watts's " Dictionary
of Chemistry," Vol. IV., p. 692.)
Electrolysis of Potassie Chlorate. KC10 3 . Molecular
weight = 122-6. According to Brester, the electrolysis of
melted potassic chlorate, with a platinum anode, yielded potas-
sium, which united with a cathode of copper or platinum.
Chlorine and oxygen, with an odour of phosphorus, were set
free at the anode, and formed thick white vapours by contact
with water (Glum. News, Vol. XVIIL, p. 145).
Electrolysis of Potassie Iodide. KI. Molecular weight
= 166'1. According to H. St. Claire Deville, silver renders a
solution of potassic iodide alkaline by simple immersion in it ;
it also liberates potassium by a similar reaction when immersed
in the fused salt (The Chemist, New Series, Vol. IV., p. 329),
I have noticed that mercury, by prolonged contact with a per-
fectly neutral solution of the salt, renders it faintly alkaline.
Faraday found that by passing an electric current through
melted iodide of potassium iodine was set free at the anode
and potassium at the cathode.
Electrolysis of Potassie Carbonate. K 2 C0 3 . Molecular
weight = 138 -2. By the electrolysis of solutions of hydro-
potassic carbonate, carbonic anhydride is very incompletely
evolved at the anode (C. Luckow, Jour. Chem. Soc., Vol.
XXXVIII., 1880, p. 283). According to Faire and Roche, in
the electrolysis of solutions of alkaline carbonates or bicar-
bonites, the molecule splits up in such a way that an atom of
potassium or sodium is set free at the cathode, and liberates
hydrogen (Chem. News, Vol. XXX., p. 63 ; Jour. Chem. Soc.,
Vol. XII., p. 861).
Electrolysis of Potassie Cyanide. KCy. Molecular weight
= 65 - l. According to H. St Claire Deville, even platinum, in
a state of fine powder, when immersed in a boiling hot solu-
tion of this salt, liberates hydrogen. By the electrolysis of a
( 130 )
solution of potassic cyanide, Kolbe observed that potassic
cyanate was formed at the anode (Watts's "Dictionary of
Chemistry," Vol. II., p. 190). Faraday noticed that the aqueous
solution yielded by electrolysis hydrogen and potash at the
cathode, but no oxygen at the anode ; that the liquid around
the anode became brown, that the fused salt, and that aqueous
solutions of potassic sulphocyanide and ferrocyanide behaved
similarly (Gmelin's " Handbook of Chemistry," Vol. I., p. 458).
Electrolysis of Potassie Ferroeyanide. KFCy. Mole-
cular weight = 368. When a solution of ferrocyanide of potas-
sium is decomposed by an electric current, ferrocyanide of
potassium is formed at the anode, and hydrogen and potash
appear at the cathode (Watts's " Dictionary of Chemistry,"
Vol. II., p. 240). The alkaline ferrocyanides yield alkali at
the cathode, and hydrocyanic acid and Prussian blue at the
anode, unless the anode is composed of copper, in which case
a deposit is there formed of cyanide of copper (Porrett, ibid.,
p. 222)
Electrolysis of Potassic Ferrideyanide. KFdCy. Mole-
cular weight = 3 29. Carbon charged with hydrogen easily
reduces a solution of ferri to ferro cyanide of potassium (Glad-
stone and Tribe, Jour. Chem. Soc., Vol. XXXIIL, 1878, p. 309).
A platinum hydrogen couple does the same readily (ibid.).
Bottger observed a similar effect with palladium containing
occluded hydrogen.
When a solution of potassic ferricyanide is electrolysed by a
separate current yellow prussiate is formed upon the cathode
(Watts's "Dictionary of Chemistry," Vol. II., p. 247).
Separation of Rubidium. Rb. Atomic weight = 85 -48.
A monad cation. Like sodium and potassium, this metal is
separated f i om its fused carbonate at a white heat by simple
contact with carbon. It was first obtained by electrolysing
its fused chloride with a graphite anode and a cathode of iron
wire. It has been obtained by electrolysing a fused mixture
of the chlorides of rubidium and calcium in their equivalent
proportions at a temperature a little below redness. It is also
obtained as an amalgam by electrolysing a strong neutral
aqueous solution of rubidium chloride with an anode of pla-
tinum and a cathode of mercury. The metal itself is decidedly
more electro-positive than potassium, and both it and its
amalgam decompose water readily (Watts's "Dictionary of
Chemistry," Vol. V, p. 129).
Separation of Caesium. Cs. Atomic weight = 132-66. A
monad cation. Unlike rubidium, potassium, and sodium, this
metal is not liberated from its fused carbonate by contact with
carbon at a white heat. An amalgam of the metal may be
easily obtained by electrolysing a solution of caesium chloride
with a cathode of mercury (Watts's "Dictionary of Chemistry,"
Vol. L, p. 1,114). M. Setterberg obtained metallic caesium
by electrolysing a dry mixture of four parts of caesium
cyanide and one of barium cyanide. This mixture fuses more
easily than caesium cyanide alone (Chem. News, Vol. XLV.,
p. 94, and Vol. XLVL, p. 249).
Separation of Ammonium (?), H 4 N lt and Electrolysis of
Ammonia. H 3 N. Weyl, in 1864, discovered that sodium
swells, liquefies, and dissolves in anhydrous ammonia liquefied
by pressure, and on removal of the pressure the sodium returns
to the metallic state ; also that potassium behaves similarly ;
that barium forms a deep blue liquid with a metallic lustre ;
and that silver, mercury, copper, and zinc likewise form un-
stable compounds with the liquefied gas (Watts's " Dictionary
of Chemistry," Vol. V., pp. 328-329). Seeley in 1870 subse-
quently discovered that metallic rubidium, potassium, sodium,
or lithium, by simple immersion in colourless anhydrous
ammonia liquefied by pressure, dissolved in the liquid, and
produced intensely blue solutions of powerfully reducing pro-
perties (Chem. News, Vol. XXIII., p. 169 ; Watts's "Dictionary
of Chemistry," Vol. VI., p. 60). I have also verified these
results, and have examined the action of the sodium solution
upon various compounds (Proc. Roy. Soc., Vol. XXI., 1873,
pp. 140, 147). In all these blue solutions it is supposed that
ammonium is set free and dissolved.
Bleekrode ascertained that anhydrous liquefied ammonia was
a conductor and an electrolyte. He passed the current from
80 Bunsen cells through it ; gas was evolved, and the liquid
became intensely blue. He also passed the current from 3,240
cells of De la Eue's chloride of silver battery through the
liquid by means of platinum wire electrodes. The anode
became black, much gas was evolved, and the liquid became
intensely blue. On stopping the current the colour disap-
peared. In these experiments ammonium was probably set
free and dissolved, and produced the colour.
Damp iron filings exposed to the air or to nitrogen induce
the formation of ammonia (Berzelius).
Electrolysis of Aqueous Ammonia. By simple immersion
of magnesium in solutions of ammonium salts, ammonia and
nitrogen are set free (S. Kern, Jour. Chem. Soc., 1876, Part II.,
p. 479). By electrolysis of ammonium salts ammonia is pro-
duced at the cathode (C. Luckow, Jour. Chem. Soc., Vol.
XXXVIIL, 1880, p. 285). According to Hisinger and
Berzelius a concentrated aqueous solution of ammonia con-
ducts as imperfectly as pure water, but by addition of a little
ammonic sulphate it is rendered easily decomposable. A gold
anode becomes covered with amber coloured fulminate of the
K2
( 132)
metal and dissolves, and the cathode is gilded. "With a
mixture of one volume of strong aqueous ammonia and three
of water, oxygen is set free at the anode, and the anode
becomes corroded. With a cathode of mercury, the bulky
" amalgam of ammonium " is obtained (Gmelin's " Handbook
of Chemistry," Vol. L, p. 458).
According to Favre, under the influence of the current,
ammonic oxide is decomposed thus : 1st, 3 (NH 4 ) 2 = 3
(NH 4 ) 2 + O 3 . The three equivalents of ammonium set at
liberty decompose the water, like potassium or sodium, thus :
2nd, 3 (NH 4 ) 2 + 3 H 2 = 3 (NH 4 ) 2 + 3 H 2 . The oxygen of
equation No. 1~ reacting upon the ammonium, gives : 3rd,
+ NH 4 = N + 2H 2 0. The first equation represents the elec-
trolysis proper (Jour. Chem. Soc. t Vol. IX., p. 985).
The so-called " ammonium amalgam " with mercury was dis-
covered in 1800 simultaneously by Seebeck in Jena, and by
Berzelius and Pontin at Stockholm. It is obtained either by
the contact of sodium amalgam with strong solution of certain
salts of ammonia, or by the electrolysis of a concentrated solu-
tion of sal-ammoniac, or certain other ammoniacal salts (not
the nitrate) with a cathode of mercury. In each case the mercury
swells to a bulky mass, which on the cessation of electrolysis
spontaneously decomposes into liquid mercury and a mixture
of two volumes of ammonia and one of hydrogen. It solidifies
below 0C., and crystallises in cubes. It does not decompose
below 29C. if previously frozen. In the separate current
process oxygen is evolved at the anode, if the salt employed is
aqueous ammonia, or the carbonate, sulphate, or phosphate,
but chlorine if it is sal-ammoniac, and but little gas is set free
at the cathode (Watts's " Dictionary of Chemistry," Vol. I.,
p. 188). If the cathode consists of spongy platinum impreg-
nated with mercury, much gas is evolved, and no amalgam is
formed (Wetherill, ibid., Vol. VI., p. 103). A concentrated
solution of trimethylamine hydrochloride behaves with sodium
amalgam just like one of sal-ammoniac (Pfeil and Lippmann,
Watts's " Dictionary of Chemistry," Vol. VI., p. 104). Various
investigators consider the ammoniacal amalgam to be merely a
spongy mixture of mercury and hydrogen (see Seeley, Chem.
Neivs, 1871, Vol. XXIIL, p. 169; also Pfeil and Lippmann,
Watts's "Dictionary of Chemistry," Vol. VI, p. 104).
Electrolysis of Nitrate of Ammonia. NH 4 NO 3 . Mole-
cular weight = 80. The action of a copper zinc couple on a
solution of ammonium nitrate showed that both nitrate and
ammonia were produced. In the cold the nitrate, even in a
solution of 20 per cent., was completely reduced to ammonia
in about 24 hours, without the escape of ammonia, free or
combined (Gladstone and Tribe, Jour. CJiem. Soc. t 1878, VoL
XXXIIL, p. 150).
( 133 )
According to Divers, dry nitrate of ammonia condenses
gaseous ammonia and becomes liquid. The liquid ammoniated
ammonia nitrate is a good conductor and electrolyte ammo-
niacal hydrogen appearing at the cathode, and nitrogen and
ammonia nitrate at the. anode. Anodes of silver, copper, lead,
.zinc, and magnesium are dissolved as ammoniated nitrates.
An anode of mercury becomes coated with an almost insoluble
compound. When the anode is acted upon the evolution of
nitrogen does not occur (Watts's i( Dictionary of Chemistry,"
Vol. VIL, p. 860; Chem. News, Vol. XXVIL, p. 37; Proc.
Roy. Soc., Vol. XXI., p. 109). Faraday electrolysed fused
nitrate of ammonium. Hydrogen gas, mixed with a little
nitrogen, was evolved at the cathode. The aqueous solution
of the salt similarly treated yielded the same mixture at the
cathode and oxygen at the anode.
Electrolysis of Ammonium Fluoride. H 4 NF. Molecular
weight = 37. I electrolysed this salt in a state of gentle fusion
by means of a current from six Grove cells, a platinum wire
anode, and a platinum sheet cathode. Conduction was copious
and heat was set free. Much gas appeared at the anode, but
no odour of ozone.
Electrolysis of Ammonia Chloride. NH 4 CL. Molecular
weight = 53'5. Hisinger and Berzelius by electrolysing with
silver electrodes a solution of this salt observed that oxygen
was evolved at the anode and hydrogen at the cathode, and
the anode became coated with argentic chloride.
Electrolysis of Ammonie Carbonate. According to See-
beck, a moistened cup of this salt filled with mercury yields by
electrolysis with the mercury as the cathode the ammoniacal
amalgam. E. Drechsel electrolysed a solution of ordinary com-
mercial ammonic carbonate, by passing a continually reversed
current through it by means of platinum electrodes during
eight hours. On evaporating the resulting liquid a salt was
obtained crystallising in fine white needles, and containing
64-69 per cent, of platinum. About O'l grain of platinum was
dissolved in 10 hours by the ammonium carbonate. By work-
ing the commutator more slowly the temperature of the liquid
rose, and by simultaneously cooling a crystalline precipitate
occurred, containing 38 -6 per cent, of platinum, and was also a
salt of a platinum base (Jour. Chem. Soc. y Vol. XXXVIII.,
1880, p. 300). B. Gerdes also electrolysed a solution of
ammonium carbonate by continually reversed currents from
four to six Grove cells and platinum electrodes. He obtained
besides ammonium nitrite and nitrate, urea, a fatty substance,
and a soluble salt of platinum (Jour. Chem. Soc., Vol. XLIV.,
p. 27).
( 134 )
Electrolysis of Sulphate of Ammonium. An^SO^. Mole-
cular weight = 132. A solution of ammonic sulphate is decom-
posed by the current, acid and oxygen appearing at the anode,
alkali and hydrogen at the cathode (Sir H. Davy). With iron
wire electrodes, hydrogen and free ammonia appear at the
cathode, and at the anode oxygen is evolved, but not until
after some time ; persulphate of iron also appears (Hisinger
and Berzelius).
Price 3s. 6d.
THE
STEAM ENGINE INDICATOR VINDICATOR DIAGRAMS.
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Edited and Enlarged by
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" THE ELECTRICIAN " SERIES
THE
ALTERNATE CURRENT TRANSFORMEI
anb
BY J. A. FLEMING, M.A., D.Sc, F.K.S., M.R.I., &c.,
Professor of Electrical Engineering in University College, London.
In Two Vols.
YOL. I. THE INDUCTION OF ELECTRIC CURRENTS.
FOURTH ISSUE. 500 pages, 157 illustrations. Price 7s. 6d., post free.
STTl^rOIFSIS OIF CO3STTEJSrT
CHAPTER I. -- Introductory.
,, II. -- Electro-Magnetic Induction.
,, III. -- The Theory of Simple Periodic Currents.
,, IV. Mutual and Self-induction.
V. Dynamical Theory of Current Induction.
Opinions of the Press on Vol. I.
" It would be very difficult to pick out from amongst the electrical literature of the past ten years any wo
which marks, as emphatically as does Dr. Fleming's book, the manner in which the practical problems of the d
have compelled electrical engineers to advance in their knowledge of theoretical science ..... It is a book whi
the electrical engineer of the present and of the future alike will read he of the present, if he can ; he of t
future, because he must." Prof. Silvanus P. Thompson in " The Electrician."
"Dr. Fleming's book contains an enormous amount of valuable matter .... which cannot be got anywhe
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YOL. II. THE UTILISATION OF INDUCED CURRENTS.
SECOND ISSUE. More than 600 pages, and over 300 illustrations. Price 12s. 6d., post fret
S"5T3STOI :J STS OIF O OUST TIE USTTS.
CHAPTER I. The Historical Development of the Induction Coil and Transforme
,, II. Distribution of Electrical Energy by Transformers.
III. Alternate-Current Electric Stations.
,, IV. The Construction and Action of Transformers.
,, V. Further Practical Application of Transformers.
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"THE ELECTRICIAN" SERIES (Continued}.
370 pages, 159 illustrations. Price 10s. 6d., post free.
HAGNETIC INDUCTION IN IRONS OTHER METALS
BY J. A. EWING, M.A., B. Sc., &c.
After an introductory chapter, which attempts to explain the fundamental ideas and the terminology, an
account is given of the methods which are usually employed to measure the magnetic quality of metals.
Examples are then quoted, showing the results of such measurements for various specimens of iron, steel,
nickel, and cobalt. A chapter on Magnetic Hysteresis follows, and then the distinctive features of induction by
very weak and by very strong magnetic forces are separately described, with further description of experimental
methods, and with additional numerical results. The influence of Temperature and the influence of Stress are
next discussed. The conception of the Magnetic Circuit is then explained, and some account is given of experi-
ments which are best elucidated by making use of this essentially modern method of treatment. The book
concludes with a chapter on the Molecular Theory of Magnetic Induction ; and the opportunity is taken to refer
to a number of miscellaneous experimental facts, on which the molecular theory has an evident bearing.
Opinions of the Press.
"Full of novel and important matter, the book is written, with admirable clearness, in a pleasant and easy
style. It abounds with references to original memoirs for the benefit of thoe who may wish to pursue the
subject further ; and in the form of tables and curves it contains a wealth of data which cannot fail to be of
value in the application of the science. It is not too much to say that no student of physics and no practical
electrician can afford to be without a copy." Mr. Shelford Bidivell in "The Electrician."
" This is one of the most important books that has appeared this year, and coming from an author of such
established reputation it will be looked upon as an undoubted authority upon the important subject of which it
treats." Electrical World (New York).
" For some time past the London Electrician has been publishing a series of excellent articles from the pen
of Prof. J. A. Ewing, whose work on magnetism is generally recognised as classical. These articles, reprinted in
book form, are now beiore us The book presents the best resume of this subject extant." Electrical
Engineer (New York).
" Das Ewing'sche Werk ist eine der werthvollsten literarischen Erscheinungen der Neuzeit und sollte in der
Bibliothek keines Elektrotechnikers fehlen."Elektrotechnische Zeitschrift.
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OF 1 CONTENTS i
Volume I. -THEORY.
rimer
No.
1. The Effects of an Electric
Current.
2. Conductors and Insulators.
3. Ohm's Law.
4. Primary Batteries.
5. Arrangement of Batteries.
6. Electrolysis.
1. Secondary Batteries.
8. Lines of Force.
). Magnets.
0. Electrical Units.
1. The Galvanometer.
2. Electrical Measuring Instru-
ments.
3. The Wheatstone Bridge.
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PRACTICAL NOTES for ELECTRICAL STUDENTS
LAWS, UNITS, AND SIMPLE MEASURING INSTRUMENTS
BY A. E. KENNELLY AND H. D. WILKINSON, M.LE.E.
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Dr. W. E. Sumpner in "The Electrician."
Fully Illustrated. Price 10s. 6d., post free.
THE
ART of ELECTROLYTIC SEPARATION of METALS
(THEORETICAL AND PRACTICAL.)
BY DR. GEORGE GORE, LL.D., F.R.S.
No other book entirely devoted to the Electrolytic Separation and Refining of Metals exists in an
language ; those on Electro-Metallurgy hitherto published being more or less solely devoted to electr<
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principles upon which the art is baaed, and the practical rules and details of technical application on a con
mercial scale, being thus suitable for both student and manufacturer.
Second Edition, price 2a. post, fret.
E L ECTRO - C
BY DR. GEORGE GORE, LL.D., F.R.S
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THE INCANDESCENT LAMP AND ITS MANUFACTURi]
By GILBERT S. RAM.
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DRUM ARMATURES AND COMMUTATORS
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FflE STEAM-ENGINE INDICATOR AND INDICATOR DIAGRAMS.
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)rmances, Expansion of Steam, Behaviour of Steam in Steam Engine Cylinders, and on Gas Engine Diagrams.
Nearly ready.
ELECTROMAGNETIC THEORY.
VOL. I.
BY OLIVER HEAVISIDE.
This work, though without the formality of a treatise, gives a connected account of the theory of electro-
nagnetism from the Faraday Maxwell point of view, and various developments of the theory. After a short
ntroduction, which is easy to read, the second chapter gives an outline of the electromagnetic connections
ccording to the Author's method of exhibiting the relations in a duplex form, symmetrical with respect to the
lectric and magnetic sides, a method which is suited for displaying the essential properties and bringing out
he true analogies, whilst it is free from the obscurities attending the use of essentially arbitrary potential
'unctions. It is also done in the Author's system of rational units, according to which the strength of a pole
s measured by the ' number of lines of force" emanating from it, which system clears away the confusion
revailing in the ordinary system. The circuital laws, the stresses and flux of energy are also considered.
lie equations are usually given in the Author's simple vector algebra, in the same form as in his previous
Electrical Papers." How to work vector analysis is explained in the third chapter, which it is hoped
nrill supply a want at the present time, as there are no treatises suitable for physical mathematics. The
lementary foundations are simply explained, and various applications given, mostly electromagnetic. This
Igebra must not be confounded with Quaternions. The fourth chapter, devoted to the theory of electro-
lagnetic waves, especially plane, is principally descriptive, and of a general nature, describing the propagation
f waves in dielectrics and the influence of conductors upon them, as well as the propagation of waves in con-
ucting media. Chapter V. consists mostly of detailed elementary examples of plane waves, calculated to
amiliarise the reader with their properties.
In Preparation, fully illustrated.
SUBMARINE CABLE-LAYING & REPAIRING.
By H. D. WILKINSON, M.I.E.E., &c., &c.
This work will describe the procedure on board ship when removing a fault or break in a submerged cable
nd the mechanical jsear U8ed in different vessels for this purpose ; and considers the best and most recent
ractice as regards the electrical tests in use for the detection and localisation of faults, and the various
iimculties that occur to the beginner.
In preparation.
ELECTRIC MOTIVE JPOWER.
By ALBION T. SNELL, Assoc.M.lNST.C.E , M.I.E.E.
The rapid spread of electrical work in collieries, mines, and elsewhere has caused a demand for a practical
ook on the subject of transmission of power. Though much has been written, there is no single work dealing
srith the question in a sufficiently comprehensive and yet practical manner to be of real use to the mechanical
r mining engineer; either the treatment is adapted for specialists, or it is fragmentary, and power work is
egarded as subservient to the question of lighting. The Author has felt the want of such a book in dealing with
lis clients and others, and in " ELECTRIC MOTIVE POWER " is endeavouring to supply it.
In the introduction the limiting conditions and essentials of a power plant will be analysed, and in the
ubsequent chapters the power plant will be treated synthetically. The dynamo, motor, line, and details will be
iscussed both as to function and design. The various systems of transmitting and distributing power by con-
;inuous and alternate currents will be fully enlarged upon, and much practical information gathered from actual
:xperien:e will be distributed under the various divisions. An especially strong chapter will be written in the
pplications of electricity to mining work in Great Britain, the Continent, and America, and the results of the
xtensive experience gained in this Held will be embodied.
In general, the Author's aini will be to give a sound digest of the theory and practice of the electrical
ran.sMiishion of power, which will be of real use to the practical engineer, and to avoid controversial points
rhich, in the province of the specialist and elementary proofs, properly belong to text-books on electricity
nd magnetism.
1, 2, and 3, Salisbury Court, Fleet Street, London, E.G.
6 "The Electrician" Printing and Publishing Company's List of Books,
"THE ELECTRICIAN" SERIES (Continued).
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THE MANUFACTURE OF ELECTRIC LIGHT CARBONS.
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gives full particulars, with many illustrations, of the whole process.
Price 2s. 6cl, post free (U.K.]
DIGEST OF THE LAW OF ELECTRIC LIGHTING.
BY A. C. CURTIS HAYWARD, B.A., A.I.E.E.
An abstract of the Electric Lighting Acts, 1882 and 1889, and of the various documents emanating from
the Board of Trade dealing with electric lighting, i'he digest treats first of the manner in which persons
desirous of supplying electricity must set to work, and then of their rights ami obligations after obtaining
Parliamentary powers ; and gives in a succinct form information of gieat value to Local Authorities, Electric
Light Contractors, &c.
Price 6s. 9d., post free.
COMPREHENSIVE INTERNATIONAL WIRE TABLE.
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of current, and length of conductors ; (2) The economies of incandescent lamps, their candle-power, potential,
and strength of current ; (3) The sectional area, diameter of conductors, and strength of current per square inch.
MAY'S BELTING TABLE.
Showing the relations between (1) The number of revolutions and diameter of pulleys and velocity of
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square section of belts at different strains per square inch.
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THE ELECTRIC RAILWAY IN THEORY & PRACTICE.
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BY H. S. CARHART, A.M.
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WORKS BY JOHN W. URQUHART.
ELECTRIC LIGHT: ITS PRODUCTION AND USE. Fifth Edition, carefully
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ELECTRIC LIGHT FITTING. A handbook for Electrical Engineers. Frilly
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DYNAMO-ELECTRIC MACHINERY:
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__^ EDITED BY H. J. DOWSING.
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ELECTRIC LIGHT INSTALLATIONS
AND THE MANAGEMENT OF ACCUMULATORS. A Practical Handbook.
BY SIR DAVID SALOMONS, BART.
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THE MANAGEMENT OF ACCUMULATORS.
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THE ELECTRIC MOTOR AND ITS APPLICATIONS.
BY T. C. MARTIN AND J. WETZLER.
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THE ELECTRICAL ENGINEER'S POCKET-BOOK
OF MODERN RULES, FORMULA, TABLES, AND DATA.
BY H. R. KEMPE, M.I.E.E.
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A HANDBOOK OF ELECTRICAL TESTING.
BY H. R. KEMPE, M.I.E.E.
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with many valuable Tables.
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USEFUL HANDBOOKS BY F. B. BADT.
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